CARNAP’S HUSSERLIAN READING OF THE AUFBAU

Jean-Michel Roy
ENS-LSH, Lyon

I. The Aufbau as a “mathesis of pure lived experiences”: 

	The distortion in the understanding of the origins of contemporary philosophy induced by its current division into a continental and an analytic trends is such that many would be surprised to learn that Carnap not only studied with attention Husserl’s major works, but also deeply appreciated them at the early stage of his thinking. Although an increasing number of historical studies (ranging from - at least –Dagfinn Føllesdal’s 1958 analysis of the relationship between Frege and Husserl  to Michael Friedman’s recent A parting of the ways ) have unravelled the complexity of the relations between the analytical and the phenomenological turns, the image of a Carnap ferociously opposed to the phenomenological movement, conveyed by his 1932 paper on the elimination of metaphysics against Heidegger , still prevails, even among well informed historians of either one of the two trends.
	In sharp opposition to this image, the little-known importance of Husserl for Carnap’s doctoral analysis of space has been brought to light a few years ago by Michael Friedman’s paper “Carnap and Weyl on the Foundations of Geometry and relativity theory” . However, to the best of my knowledge, no real attention has been paid so far to the fact that in his later Aufbau , Carnap also significantly refers to Husserl’s Logische Untersuchungen (1900-1901)  as well to the first volume of Ideen zu einer reinen Phänomenologie und Phänomenologischen Philosophie (1913) , to the point that he himself suggests a Husserlian interpretation of the constructional system offered in his own book. Indeed, in § 64, Carnap explicitly indicates that the elementary lived experiences  (Elementarerlebnisse) which constitute the basic elements of this system are similar to the pure lived experiences (reinen Erlebnisse) disclosed by Husserl’s transcendental reduction, and which constitute the specific domain of the phenomenological science that this reduction is intended to make possible: 

“ At the beginning of the system, the experiences must simply be taken as they occur. We shall not claim reality or non reality in connection withy these experiences; rather, these claims will be ‘bracketed’, i.e. we will exercise the phenomenological ‘withholding of judgment’, epoche, in Husserl’s sense (Ideen I, §§32-33)” . 

It is apparently legitimate, therefore, to see the Aufbau as offering the outline of a constructional system of a transcendental kind, in Husserl’s sense of the transcendental; in other words, as offering a logical construction of scientific natural reality on the basis of the specific domain of being that Husserl calls the region of pure lived experience, and sees as constituting such reality. 
	The fascinating point, however, is that Carnap thereby assimilates his constructional system with an epistemological type of phenomenology that, in reality, Husserl explicitly puts aside in §§ 71-75 of his Ideas I. As a matter of fact, immediately after stating that the Aufbau’s fundamental goal is to solve “the problem as to how scientific concepts are to be reduced to the ‘given’”, Carnap writes: “There is a connection with the goal which was proposed by Husserl, namely his ‘mathesis of [lived] experiences’ (Phän., 141-§75)”. However, such a mathesis is an axiomatic or more geometrico form of investigation of lived experiences - more accurately, of pure lived experiences - that Husserl considers as inadequate, and against which he advocates “ a purely descriptive” form of investigation. The epistemological characteristic of this purely descriptive approach is to provide all statements about pure lived experiences with an immediate justification, and, consequently, to make (almost) no use of formal logic. It is important to note that in Ideas I such a mathesis of pure lived experiences is not declared, however, to be impossible, and that § 75 of the book explicitly leaves the problem of its scientific relevance and actual feasibility unsolved. It is therefore also legitimate to read the Aufbau as pretending to answer Husserl’s perplexity on the issue by offering, if not a fully axiomatic kind of investigation of pure lived experiences - of phenomenology -, at least a crucial component of it, namely a transcendental constructional system.
	Assuming that this interpretation of Carnap’s 1928 attitude towards Husserl is correct, as I think it is, two main questions naturally arise. The first one concerns its validity: Is such a Husserlian reading of the Aufbau, suggested by Carnap himself, a tenable one ? Can we really see Carnap’s first major work as offering the basic component of a mathesis of pure lived experiences? The second question deals with the motives underlying the divergence between Husserl and Carnap in the choice of the epistemological form of the investigation of pure lived experiences: why does Husserl reject an axiomatic and, consequently, a constructional approach, while Carnap embraces it ?
	In a previous effort to answer these questions , I defended the following view. On the one hand, Carnap’s suggestion that the Aufbau is a first step towards a Husserlian mathesis of pure lived experiences is unacceptable because, although his notion of axiomatic knowledge fits in broad outline Husserl’s one, his ‘elementary lived experiences’ cannot really qualify as pure lived experiences, in spite of their pretension to ontological neutrality. On the other hand, Husserl’s rejection of an axiomatic form of investigation of pure lived experiences is a consequence of his definition of phenomenology as a scientia prima, which implies that formal logic should be founded upon phenomenology and cannot therefore be put to use by it. In other words, I advocated that, from a Husserlian point of view, a ‘mathesis of pure lived experiences’ is in fact prohibited for architectonic reasons, adding that such prohibition, which stands in direct opposition to § 107 of Aufbau where Carnap acknowledges expresso verbo the necessity for the preliminary construction of logical objects, represents a major point of departure within early twentieth century philosophy. This is where Rhine and Danube, to play with Dummett’s beautiful metaphor, start heading in different directions.
	Disregarding here entirely this second issue - which was my major point of interest in the study just mentioned -, I wish to consolidate my negative conclusions as to the validity of Carnap’s Husserlian interpretation of his Aufbau by reconsidering the question from a new angle. As indicated in § 3 of the book, the main reason sustaining Carnap’s claim that he offers a mathematical form of Husserlian phenomenology is his assumption that Husserl’s phenomenology aims at a reduction to the given similar to the one that he himself tries to achieve. I wish to show that this assumption is unwarranted, and thus based on the ignorance of substantial differences, dissimulated by apparently striking similarities, between the two enterprises. More specifically, my own claim will be that, even if Husserl had admitted the possibility of a mathesis of pure lived experiences, and if Carnap had indeed taken pure lived experiences as a basis for his system, the Aufbau would still not qualify as a contribution to a Husserlian mathesis of pure lived experiences, because it is pursuing a kind of reduction to the given which, appearances notwithstanding, is deeply alien to Husserl’s phenomenology. In addition, I will also suggest that the only way in which the system of the Aufbau and Husserlian phenomenology could converge is by making the latter a foundation of the former. Indeed, Husserlian phenomenology can provide the theory of the epistemic order required by the sort of epistemic constructional system sought for in the 1928 book.
	Accordingly, I will proceed by way of a systematic confrontation of Carnap’s notion of ‘reduction to the given’ with Husserl’s injunction “to return to the things themselves”, which, upon examination, proves to be an injunction to “ return to the given”.

2. Carnap’s reduction to the given:

Before setting to analyze the exact meaning of Carnap’s idea of a reduction of all scientific concepts to the given, a task that involves reviewing basic but not uncontroversial aspects of the Aufbau, the extent to which Carnap really aims at such a reduction, and the reasons why he does so, must first be examined.
	In fact, the Aufbau pursues a general and a particular goals, and the reduction to the given only corresponds to the second one. This particular goal needs however to be grasped on the background of the general one in order to be properly understood.

	21. The general goal of the Aufbau:

	At its most general level, the Aufbau is a book in what Carnap calls construction theory . As such, its ambition is to establish the possibility of a constructional system of all non-formal scientific concepts, as well as to specify the logical conditions of its realization. Indeed, Carnap writes that “ the basic assumption of construction theory is the possibility of a unified constructional system” . According to him, construction per se is a matter for scientific research itself, and construction theory cannot go beyond providing a schematic illustration of what a constructional system looks like , such as the one to be found in Part III of the Aufbau.
A constructional system is defined as a system of scientific concepts deriving its systematic unity from the fact that all the concepts involved in it are logically derived from a few primitive ones. Establishing the possibility of a constructional system is therefore conceived by Carnap, as clearly indicated in § 4 of the Aufbau, as a first step towards establishing the broader thesis of the unicity of non formal science, that is to say, the thesis that non formal science not only has unity, but a unity that makes it one single scientific theory. Carnap insisted on several occasions  that an additional step is necessary for obtaining this broader thesis, namely showing the deducibility of all non formal scientific propositions from a restricted set of axioms. The Aufbau represents therefore his first attempt to demonstrate the constructional side of the thesis of the theoretical, or axiomatic, unicity of empirical science, by drawing on the resources of the “new logic” of Frege, Russell, Whitehead and Wittgenstein, and by taking as a model what these philosophers achieved for logic and mathematics. 
As such, the Aufbau is not concerned with any kind of reduction to the given, but is a foundational - although not necessarily foundationalist - enterprise, and consequently an epistemological one. The unification of empirical science into a unique axiomatic system is indeed intended as a way of clarifying and reinforcing the ultimate reasons we have for believing in the adequacy of its propositions. The search for axiomatization and constructional unity is a search for a maximized degree of rational justification, and hence for maximal certainty. In other words, the most general goal of Carnap’s 1928 construction theory is to show that the progress of modern logic make it possible to solve the problem of the foundation of empirical science, after solving the problem of the foundation of formal science.
	This foundational thesis is associated with three additional ones, to which the theory of the Aufbau owes much of its originality.
	First comes the thesis of the reductionist character of logical derivability, as well as the further thesis of the ontological unity of science following from it. Indeed, Carnap’s well known idea is that, in a constructional system, every concept is derivable from a set of basic ones to the extent that it is extensionally identical with a logical construction of these basic concepts, and is, in that sense, reducible to them. In the terminology of  § 35 of Aufbau, every propositional function exclusively about a concept of the system is coextensional with a propositional function exclusively about the basic concepts of the system. As a result, the only entities postulated in a constructional system are the kind of entities referred to at the level of the basic concepts, and empirical scientific knowledge is not only conceptually unified, but also ontologically unified. It has a single domain of investigation. In § 6, Carnap writes: “ the fundamental thesis of construction theory… asserts that there is only one domain and that each scientific statement is about the objects in this domain”.
	Carnap actually goes much beyond the assimilation of logical derivability with logical reduction or logical construction: he also contends that the new logic demonstrates “the mutual reducibility” of the concepts of the empirical sciences. His claim is that there is no unique way, from a purely logical point of view, of introducing a reductive order within those concepts, thereby opening the possibility for empirical science to be founded on various alternative kinds of primitive propositions. This principle of constructional tolerance has the obvious consequence of introducing a certain form of ontological relativity: what there is in the world from a scientific point of view depends on the constructional order adopted, since there is nothing more in the world than what is postulated in the basis of the constructional system adopted. When conjugated with the further idea that the notion of ontological order makes no sense independently of that of a constructional order, Carnap’s principle of constructional tolerance results in a strict form of ontological relativity.
	Finally, Carnap also introduces the thesis of the formality of empirical science, to the effect that empirical science is only concerned with the structural properties of its objects, understood as their relational properties of a formal kind. As a consequence, the unique domain dealt with in a constructional system is only known by means of structural descriptions  of its elements, and all concepts are logical constructions of basic structural descriptions. As a matter of fact, Carnap insists that a constructional system only deals, in its final form, with logical properties, although it refers, through these logical properties, to non logical ones. His motivation for adopting the further thesis of the formality of empirical science is that he sees it as the only way to secure its objectivity. It should be noted that his argument on this point rests crucially on the fact that a reduction to the given is one of the constructional possibilities. The given being something subjective, if empirical science can be seen as concerned with material properties and not formal ones, it is in principle reducible to something subjective.
	
22. The special goal of the Aufbau:

	This is the only way in which construction theory, when considered at its most general level, shows any particular connection with a constructional system based on the given, which is otherwise no more than one constructional option among many others. However, the Aufbau also has the more specific ambition to advocate a constructional system of a specific kind, and it is only in relation with this more specific ambition that the notion of a reduction to the given acquires special importance. And also that Carnap makes comments about the existence of a common goal between construction theory and Husserl’s mathesis of pure lived experiences. In other words, it is only sub specie that construction theory is considered as converging with Husserl’s phenomenology.
	Carnap’s more specific ambition results from his willingness to have the constructional order of a constructional system follow what he calls the epistemic order of concepts, as well as of what these concepts refer to. Something is said to be epistemically – one should probably say today cognitively – secondary to something else, if its recognition presupposes the recognition of that other thing . In other words, in a constructional system of an epistemic kind, the order of reduction is constrained by the order of formation or acquisition of concepts, or more accurately, by a schematized or idealized version of such order. Indeed, elaborating on a remark of § 54 of the Aufbau, Carnap writes in his “Intellectual Autobiography”: “ Although I was guided in my procedures by the psychological facts concerning the formation of concepts of material things out of perceptions, my real aim was not the description of this genetic process, but rather its rational reconstructional, i.e. a schematized description”. In contradistinction to the constructional order, the epistemic order is however implicitly assumed by Carnap to be unique and to start with what is given, forcing therefore an epistemic system to renounce the principle of constructional tolerance and to take the given as a basis. 
Construction theory is thus concerned with a reduction to the given only to the extent that it is concerned with the project of elaborating an epistemic system. Although Carnap does not elaborate on this point, his reasons for being specifically interested in this kind of system are clearly of an epistemological nature. Such a constructional system not only contributes, like any other one, to solving the problem of the foundation of empirical scientific knowledge, but it also contains a theory of the acquisition (genesis) of knowledge, and a theory which, in addition, is consonant with the foundational solution being proposed. Furthermore, thanks to the thesis of the formality of science, Carnap can also pretend to explain, by means of an epistemic kind of constructional system, how something objective can be grasped by something subjective.
	The specificity of the particular kind of epistemic system that he opts for depends mainly on the nature of its basis. It is therefore necessary to clarify how Carnap understands the notion of given.  Two questions should here be carefully distinguished. The first one is: what does it mean for Carnap to be given? In other words: What does givenness mean for him ? And the second is : what does satisfy this definition in his opinion? In answering the second question, it will appear that an epistemic constructional system requires a preliminary investigation of the given, thereby opening on the question of the possibility of a convergence of the Aufbau with Husserlian phenomenology a perspective different from the one voiced by Carnap himself. 

	23. Givenness and given:
	
	The notion of given is explicitly introduced in § 64, in an effort to further specify that of autopsychological element: 

“…within the autopsychological realm, the basis must be more precisely delimited… all experiences belong to it, whether or not we presently or afterward reflect upon them. Thus we prefer to speak of the stream of experience. The basis could also be described as the given...”. 

The notion of given is here taken as nearly synonymous with that of experience, although Carnap claims to prefer the first notion because it has “the advantage of a certain neutrality” . In fact, this statement sounds more like a definition of what is given than a definition of what it is to be given, and the notion of experience is, in addition, left unspecified. § 67 contains however a crucially illuminating remark, stating that an epistemic system “starts from what is epistemically primary, that is to say the given”. Here, the notion of given is specified by means of the notion of epistemic priority, and it is revealed that being given or givenness such notion means nothing else than the fact of being epistemically primary. It follows that can itself be considered as nearly synonymous with it.
	On the basis of this definition, Carnap introduces a further and important distinction between the given and the given as such (“the given as it is” ). The given is not simply what is epistemically primary, but what is epistemically primary as such: in other words, not every determination of what is epistemically primary is itself epistemically primary. Such is the case, from Carnap’s viewpoint, with the components of the given, or with properties that are simply indissociable from it without being themselves given, such as the fact of belonging to a subject. Determinations of this kind are called ‘abstractions’ from the given as given, an abstraction being precisely defined as “something that is epistemically second”. 
What is endowed with the property of givenness so defined ? What is epistemically given as such ? However natural, this question seems nevertheless largely an illegitimate one from the point of view of construction theory. 
Indeed, whatever is at the basis of a constructional system is said to be neutral with regards to properties introduced at a later stage, in the sense that these properties cannot be predicated positively or negatively of the basis as such. Otherwise it would not be the basis of the system. Neither can the basis as such be characterized by means of any of these properties, once they have been introduced, since they are by definition determinations that the basis does not have as a basis. There is therefore something ineffable about the basis of a constructional system, as Carnap explicitly acknowledges in § 65, where he writes: “…before the formulation of the system, the fundamental elements are without properties, and do not fall into specific domains”.  This assertion cannot be of course litteraly true, since it would imply the impossibility of erecting any constructional system at all. Carnap expresses therefore his views more adequately when, later in the same paragraph, he mentions the existence of an “original property” of the basis. 
As a matter of fact, within the basis of a system, he introduces a further distinction between the basic elements and the basic relations in which these basic elements stand to each other. And he takes the original properties just mentioned to be precisely those expressed by such basic relations, or, more accurately, by the structural characterization of these relations:

 “ [The basic relations], and not the basic elements, form the undefined basic objects (basic concepts) of the system, and all other objects of the system are considered from them. As far as construction is concerned, the basic relations take precedence over the basic elements which are their members: generally speaking, construction theory considers individual objects as secondary relative to the network in which they stand”. 

Accordingly, the only thing that can be properly said of the basis as such of a given system is whatever the basic structural characterizations of the basic elements say of them. Any other statement about them is improper from a constructional point of view.
When applied to the system of the Aufbau, where the given as such constitutes the basic element and where the only basic relation acknowledged  is that of recollection of similarity, these considerations imply that the only legitimate way to answer the question: what is the given as such ? is to say that it is whatever has a property that is epistemically primary, as well as a recollection of similarity with something else (or more accurately: whatever satisfies the structural characterization of the recollection of similarity).
It should not be concluded, however, that no indication can be provided about the nature of the basic elements of a constructional system. And Carnap himself does provide a number of such indications about the basic elements of his own system (especially in the chapter entitled “The basis”): but these indications cannot be legitimate characterizations of the basis from a standard constructional point of view. Carnap’s indications are of two main types: one type consists in anticipating on the determinations of the basis to be introduced at a later stage, and the other in adopting the point of view of the pre-constructional system of concepts (of “the old system”, as Carnap calls it), and therefore an external one. The indication that the given is autopsychological belongs for instance to the first type, while the statement that it should not be confused with sensations and instead be assimilated with what Gestalt psychology calls a total impression is an example of the second kind, while the assertion that the given is subjectless can be viewed as a mixture of both. These indications provide an intuitive identification of the nature of what is epistemically primary. And it is in the context of providing such indications that a few positive and negative comparisons with Husserlian phenomenology are made by Carnap, including the important one about the ontological neutrality of the given previously mentioned (cf supra § 1). Accordingly, these remarks about Husserl should apparently be read as being no more than an indirect specification or indication of what the given as such is.
This interpretation of the status of Carnap’s remarks about Husserl is, however, insufficient. As a matter of fact, there is something peculiar about constructional systems of an epistemic kind, that calls for a different analysis of the determination of the nature of their basic elements. Indeed, these systems are necessarily dependent upon a preliminary analysis of the epistemic order which they are intended to reflect, and a crucial aspect of this preliminary analysis consists of course in deciding on what is epistemically primary as such, that is to say on what is given as such. In a non epistemic constructional system, the basis is determined on purely constructional grounds: it is nothing else than what makes the construction of all other concepts possible, and only considerations of “logical performance” come into play when deciding about it. Accordingly, from the point of view of construction theory, nothing legitimate can be said about the nature of the basic elements beyond what is said about their structural properties at the basic level of the system under consideration. In an epistemic system, on the contrary, the choice of the basis is dependent upon epistemic considerations which are by themselves independent of constructional considerations. The question : what is given or epistemically primary as such ? is therefore a legitimate and necessary question to ask for construction theory, even though construction theory itself cannot answer it. If it could, the system in question would still be an epistemic one, although in a different sense : the constructional order itself would determine the epistemic one. 
As a consequence, it is in fact impossible to view Carnap’s efforts to answer this question, and the references he makes to Husserl in that context, as mere auxiliary indications designed to give an intuitive understanding of what is given as such, by either drawing on the old system of concepts or anticipating on the development of the new one. Even though Carnap does not make it fully clear that construction theory requires a preliminary investigation when it comes to choosing the basis of an epistemic system. He also leaves pretty much in the dark what the nature of this investigation might be. 
He actually contents himself with borrowing from a mixture of theories, Husserlian phenomenology being just one of them, and in the end gives no more than a sketchy image of the nature of what is, in his eyes, epistemically primary as such.  It is to be understood as a stream of global sensory experiences, akin to what Gestalt psychology calls total impressions, and divisible in different ways into elementary segments, famoiusly called “elementary experiences”. As such, those elementary experiences are anterior to any subject-object structuration, as well as to any division into sensory elements and to any distinction between reality and non-reality. 
Despite the lack of precision of this description, an important conclusion clearly emerges: there is no principled obstacle for Carnapian construction theory to be founded on Husserlian phenomenology, if Husserlian phenomenology can provide a determination of what is epistemically prior as such, and an adequate one. 

3. The first step of Husserl’s return to the given: the principle of intuitionism

To what extent is the theme of a reduction to the given present in Husserlianism, and if so, how much does it differ from the Carnapian one ? Although Carnap only makes reference to Husserl’s phenomenology, phenomenology is just one component of husserlianism, and the problem must therefore be addressed in two successive stages: one dealing with Husserl’s general theory of knowledge, and the other dealing with phenomenology per se. The distinction is in some way only a relative one, since the theory of knowledge ends up being entirely absorbed into phenomenology: it is however an important one to respect in order to disentangle the relations between Carnap’s and Husserl’analyses of the given and of its epistemological role.
	The most obvious remark to start with certainly is that, while Carnap does not have anything resembling a real theory of both givenness and the given, in spite of the necessity for it just emphasized, Husserl elaborates a quite detailed, sophisticated and central one, as early as the first edition of his Logical Investigations. This theory, then, precedes in time the invention of phenomenology stricto sensu (ca 1904). In fact, it is also antecedent to it from a logical point of view, since it plays a crucial role in discovering the transcendental intuition on which phenomenology is entirely based, and even though it is at a later stage reintegrated into phenomenological theory. 
A central characteristic of the content of this theory of givenness and of the given as such is that it takes the form of a theory of intuition, and furthermore, of an intuitionism, understood as an epistemology based on intuition. The fundamental principle of this intuitionism is most clearly stated in § 1 of Ideas I as follows: “ Every science has its own object-domain as field of research, and all knowledge contained in it find their source and foundation in certain intuitions in which objects of the domain are given, and in part at least, in the form of originary data (zu originärer gegenbenheit)”. Husserl further specifies that “ the giving (Gebende) intuition is, for the first and natural sphere of knowledge and all of its sciences, natural experience; and the originary giving lived experience is perception in the ordinary sense of the term”.  Accordingly, every knowledge originates in an intuition of a given, and this intuition is also what provides it with a rational justification. Such intuitive justification can of course be either immediate or indirect, that is, obtained by means of mediating inferences. In other words, Husserl retains the classical view – dating back at least from Aristotle’s Second Analytics – that a theory is an axiomatic system ultimately rooted in intuition. Such intuitionism is what gives its fundamental meaning to Husserl’s famous injunction to go back to the phenomena. Although this injunction also has the broader sense of inviting us to limit all of our claims to what we are intentionally related with just as we are intentionally related with it, it is first and foremost an invitation to limit our claims of knowledge to claims that can be ultimately grounded in a giving intuition. Accordingly, it must be understood as an invitation to give scientific theories the form of a rigorously axiomatized system rooted in self-evident primitive propositions, an epistemological perspective very close to the one incarnated by the special goal of the Aufbau, since it means that science should be axiomatically based on propositions about something given.
	The details of Husserl’s intutionism are vast and complex and only its most essential aspects need to be briefly reviewed here. Crucial to it are two kinds of distinctions introduced into the content of intuition, and referring respectively to differences in the objects intuited and to differences in the manner how these objects are intuited .
	The fundamental division between intuition and originary intuition belongs to the second kind. Intuition is an intentional state or act which, by contrast with non intuitive intentional acts, gives its object in the sense that the subject is related with the object itself, directly and not through another, intermediary, one, such as a sign. An originary intuition gives its object not only directly or “in person”, but as real, as actually present: such, for instance, is the difference separating perception from imagination. 
Within the first kind, three essential oppositions must be mentioned:
a) The opposition between the intuition of individual objects and that of general or eidetic ones (essences), which sharply differentiates Husserlian phenomenology from empiricism. In Husserl’s eyes , empiricism results from a misguided application of the principle of intuitionism, unduly limiting it to empirical intuition;
b) The opposition between intuition of material essences and intuition of formal essences, which serves respectively as the source and foundation of two different types of eidetic or a priori sciences:
c) The opposition, within material intuition – individual or eidetic – between external intuition, which delivers spatio-temporal objects (physical things, or essences of), and internal intuition, in which only temporal objects (psychological elements, or essences of) are given (in fact these objects are also spatial, but only in a indirect manner). It is important to note that, because of the directly or indirectly spatial nature of their objects, material intuitions of an individual kind are considered to be not purely intuitive, but a mixture of intuitive and non-intuitive elements.
	Finally, it is unclear whether Husserl ever managed to give a satisfactory account of the difference between a giving or intuitive intentional act, and a non-giving or non intuitive one. His early fifth Logical Investigation is probably where he addressed the issue most technically. According to the analysis defended in this text, the opposition between intuitive and non intuitive intentionality is ultimately a matter of “form of apprehension”, by the material component of the intentional part of an intentional act (the noesis in the 1913 terminology), of its non intentional part (the hyle in the 1913 terminology).
	
4. Two forms of intuition based axiomatization:

	The previous paragraphs have put into light a major similarity between the special goal of the Aufbau and the general project animating Husserl’s theory of knowledge: both of them aim at a rigorous axiomatization of scientific knowledge on the basis of a given. A first confrontation of their respective notions of givenness and given as such is then now possible.

	     41. Husserlian givenness and Carnapian givenness:

Being the source and foundation of knowledge, the Husserlian concept of givenness and given clearly shares the two central features of the Carnapian one; namely, being what is epistemically primary and acting as the conceptual basis of the constructional system of non formal sciences. However, the importance granted to these two factors stands in sharp contrast in both authors: the first one is seen as the essential characteristic of being something given by Carnap, but not by Husserl, and conversely, the second one is seen as essential by Husserl, but not by Carnap. 
	Beyond these similarities, the Husserlian notion nevertheless possesses a number of determinations which are absent from the Carnapian notion:
1. Being an intentional object: The most fundamental one is probably the fact that the given is for Husserl a kind of object, and therefore cannot be dissociated from an intentional structure with a subject pole, as Carnap himself remarks in a critical manner in the Aufbau. The implication is that the Husserlian given can at no stage be considered as something intrinsically subjective, contrary to the Carnapian given, which, at a certain level  of construction, falls under the concept of “autopsychological element”. The given is a category that can only be applied to the intentional object, and Hintikka’s attempt, in his article “The phenomenological dimension” , to interpret the hyletic data as what is essentially given in an intentional state is for that reason misguided.
2. Incarnating the fundamental form of objectivity: Not only is the Husserlian given an object, but it also is the most fundamental form of objectivity. An object is first and foremost what can be intuited. Husserl writes that the two concepts of intuition and object are “correlative”.
3. Being an intuited object: The specificity of this fundamental form of objectivity is described as the fact that the object is intuited, that is directly apprehended by the subject of the apprehension, in an unmediated way, and, in the fundamental case of originary intuition, as being real (present). This is the distinctive feature of the Husserlian notion of givenness, and therefore the essential one. It is important to underline that the Carnapian notion of epistemic primacy does not per se involve the notion of being unmediated in the Husserlian sense, even though the elementary pure experiences arguably have that determination. More generally, the notion of intuition plays no role in Carnap’s analysis of the given, even under a different definition.
4. Having essentially a foundational role: Finally and most importantly, the Husserlian given is intrinsically the foundation of scientific concepts, while the Carnapian given is just one such possible foundation among several others. In other words, Husserl’s intuitionism is a foundationalism in the general sense of a theory of knowledge admitting that a certain subset of knowledge has a foundational role in virtue of its content, and not only in virtue of its logical power to sustain the rest. Accordingly, although both Carnap and Husserl seek a rigourous axiomatization of scientific knowledge based on propositions and concepts referring to something given, they do so in a fairly different spirit.

	42. Husserlian given as such and Carnapian given as such:

	These differences in the definition of givenness are correlated with at least two important differences in the determination of what is effectively given as such. 
One is the fact that what is given is, for Husserl, not holistic in the sense in which it is for Carnap: in the reflexive internal intuition of an intentional perceptive act, for example, the elementary components of the perceptive act, such as hyletic data, are no less given than the perceptive act itself. However, Husserl also clearly accepts the non Carnapian idea that some given elements are epistemically prior to others (e.g. the intuition of individuals is prior to the intuition of essences), and that the notion of epistemic priority is therefore a relative one. Carnap cannot, of course, accommodate such relativity, since epistemic primacy is for him the defining feature of the given.
The other and more crucial one lies in the diversity of the Husserlian given, which includes different kinds of objects, individual and general, formal and material, external and internal. By virtue of the principle of intuitionism, admitting such diversity is tantamount to admitting ontological pluralism, a position which stands in direct opposition to Carnap’s ontological “monism” of the given in the Aufbau. From Husserl’s perspective, going back to the given opens the doors of a universe richer than the one postulated by standard sciences; from Carnap’s perspective, it opens the doors of a much impoverished one. Since the principle of intuitionism also says that each kind of intuited object delineates a specific domain of investigation, Husserl’s ontological pluralism also implies the diversity of scientific domains, and consequently, the disunity of science – at least in the Carnapian sense of the unity of science. In a revealing moment of § 17 of Ideas I, Husserl writes: “… there emerges the idea of a task that is set us: to determine within the circuit of our individual intuitions the highest genera of concreta, and in this way to effect a distribution of all intuitable individual being according to regions of being, each of which….marks off on lines of principle an eidetic and an empirical science”.
The important conclusion to be drawn from this confrontation of the Carnapian and Husserlian analyses is that, beyond the differences separating their definition of the idea of givenness, they are linked with strikingly opposed views about what satisfies this definition. As a result, an essential condition for making Husserl’s notion of return to the given close to, or at least really consonant with, Carnap’s notion of reduction to the given is missing. 
The difference between them can nevertheless only be an insuperable one if the ontological diversity acknowledged on the basis of the principle of intuitionism by Husserl is irreducible. Husserl asserts that it is so, but does not support his assertion with any argument in the previous quotation.
There are at least two possible ways of justifying it. In the first place, it is in the logic of the principle of intuitionism that the irreducibility of the kinds of objects intuited (and the corresponding scientific domains) be itself considered as something given. In the second place, even if it were possible, in Husserl’s opinion, to build a system where given elements of a certain kind were reduced to given elements of another kind, such a constructional system would not be adequate, precisely because it would not be as completely based on intuition as it should. Which is to say that, even if Husserl had fully integrated the constructional possibilities opened up by the progress of logic, he would have stuck to the thesis of the irreducibility of scientific domains because of his theory of the nature of the given as such. Husserl’s theory prohibits the sort of unifying axiomatization of non formal science on intuitive grounds that Carnaps’s epistemic constructional system is aiming at.

    43. Logical construction and reducibility:

Finally, there is an additional obstacle between the two projects of axiomatizing scientific knowledge on the basis of the given, coming from the notion of logical derivation itself. In the Husserlian framework, the clarification of this notion belongs to formal (objective) logic, and more specifically to one of its main divisions, the theory of multiplicities or deductive systems. It is clear from Husserl’s central exposition of this theory that, in his opinion, the specific feature of a theoretical or axiomatic knowledge lies, quite classically and as already emphasized, in the fact that concepts and propositions contained in such knowledge are logically derived from primitive ones. And a domain is a theoretical one or a multiplicity, if it is amenable to such knowledge. The domain of phenomenology, for example, is not, in contrast to the domain of geometry.
Although Husserl does not openly criticize any notion of logical reduction akin to the Carnapian one in his central writings, and although he also occasionally makes use of the notion of logical construction to designate the logical derivation of one concept from another, his approach to logical derivation is clearly non reductive. Like intuition, logical construction is for him an instrument of ontological enrichment, and not an Ockamian tool of ontological economy. One reason is that the notion of logical form has for him an ontological dimension, contrary to Carnap; deriving a logical construct is deriving a new ontological entity of a formal kind. Another reason is that constructed entities are also in his opinion materially distinct from their basis: in an axiomatization of physics on the basis of the notion of particle, for instance, there is definitely more, from the point of view of Husserl, in the concept of atom – and correspondingly in the atom itself - than a logical bundle of particles. In short, if Husserl also believes that all scientific concepts are to be logically derived from concepts referring to the given, in no way does he think that a logical difference is exclusive of an ontological one, both formally and materially.

5. Husserl’s second step: the requirement of a scientia prima:

The confrontation carried out so far yields a clear-cut result: beyond a common interest for a more rigorous axiomatization of scientific knowledge on the basis of something given, as well as common elements in their notions of givenness, Husserl cannot share Carnap’s concern for a unique axiomatic and constructional system, for essential reasons dealing with both his theory as to what is given and with his theory of logical construction. 
The confrontation must nevertheless be carried out one step further, because Husserl does not think that axiomatisation alone can solve the problem of the foundation of knowledge. It is his contention that what is also needed in order to solve it is an understanding of the fact that a subject can grasp the objectivity of an object, and more importantly, that a subject can have an intuitive grasp of an object. Like Frege, Husserl considers what he calls “the relation of knowledge” to be an enigma , but an enigma that he nevertheless also considers, in sharp contrast to Frege, as necessary to solve, and, in no less sharp an opposition to Carnap, as impossible to solve by purely axiomatic means. In other words, what is equally needed, according to Husserl, is a foundation of the axiomatic foundations of science, because axiomatization makes an uncritical or naïve use of the notion that an object can be given, and more generally apprehended as it is. And the central goal, as well as historically the first one, of the new phenomenological science that Husserl strives to develop is to provide such a foundation, thereby necessarily occupying the root place in the tree of knowledge and pretending to the title of scientia prima. As a result, a new question arise: is phenomenology itself in any way connected with the notion of a reduction to the given, and if so, how does this notion differ from Carnap’s notion? And also: what are the consequences of this new problem for the conclusions just obtained ?

    51. The necessity for a return to the pure given:

The status of first science granted to phenomenology immediately entails that, if there is such a thing as a phenomenological reduction to the given, this phenomenological reduction must also be of a substantially different nature from Carnap’s reduction. Indeed, having to provide formal logic itself with a foundation - a part of phenomenological investigation that Husserl calls transcendental logic -, phenomenology cannot make use of its resources, as it was already briefly indicated. And this is the reason why, even if the domain of phenomenological investigation were a multiplicity, phenomenology could not take the form of a “mathesis of pure lived experiences”. In other words, phenomenology cannot be, like construction theory, “ an applied logistics”. 
It is actually well known that phenomenology is, and in a very deep and substantial way, connected with a notion of reduction to the given. Husserl’s famous transcendental reduction is indeed such a reduction, as well as what makes phenomenological investigation possible by providing it, in strict accordance with the principle of intuitionism, with a specific intuition and a specific domain.
Every reduction is in a certain sense an elimination, since it consists in reducing something to something else. In the present case, the reduction consists fundamentally (it is in fact a complex process, involving different stages, and encompassing the whole of scientific reality, individual and eidetic, material and formal) in reducing what is given as real in the originary intuition of individual spatio-temporal objects (transcendent intuition) to a simple phenomenon, and it is obtained by merely suspending the belief in reality which is intrinsic to such intuition, and as such, antepredicative. By virtue of this suspension or epoche, which is also antepredicative, the object given as real is not negated, but simply put into brackets: it just does not count anymore. When applied for instance to the perception of a tree, it means that we stop believing that we see a real object, different from us and located in external space and time, as well in fact as in the reality of the psychological operation of seeing the tree. Instead, what is apprehended by us are mere phenomena of physical and psychological realities. 
The essential point of the transcendental reduction is that, although it can in principle be unlimited, it has in practice no reason to be. The reason for making use of the possibility of suspending the spontaneous belief in the reality of what is given in a transcendent individual intuition is that such intuition represents an impure form of intuitive act (cf. supra): whatever is given in it is surrounded by non-given determinations, thereby opening the door to rational doubt. But once the content of intuition has been transformed into a mere phenomenon, Husserl claims that the phenomenon itself can in turn, by means of an additional intuitive act of a reflexive nature, be intuited as something real, although incarnating a new kind of reality. On the one hand, it is dissociated from any real spatio-temporal entity - since all of them have been “put into brackets” -, and on the other hand it is thoroughly given, offering no good motive for suspending again the antepredicative belief also inherent to the new “immanent” intuition.
As a result, not only is the transcendental reduction a reduction to a given, in the generic Husserlian sense of something intuited, but it is a reduction to a new kind of given, both from the point of view of the nature of what is given and from the point of view of how it is given. What is given is a “pure” lived experience, in the sense of a lived experience “disentangled’ from physical reality or purified from any connection with it, and especially from the intentional relation with spatio-temporal objects and the embodiment relation. But a pure lived experience is also pure in the sense of being purely and therefore absolutely given, making phenomenology not only a scientia prima but also a scientia absoluta.
Finally, Husserl goes one step further by making, in addition, phenomenology a transcendental science, in the sense that it is also characterized as an investigation of the constitution of the elements of all domains of reality, individual or eidetic, by the elements of its own domain, namely pure lived experiences. Indeed, according to Husserl’s radical form of transcendental idealism, whatever is, is, and is what it is, by virtue of some processes animating pure lived experiences. The tree that I see, for instance, is entirely relative to “pure” perceptual processes and is nothing independently of them. And it is precisely the task of phenomenology to unravel the nature of this constitutive processing. A task that it performs by assuming the form of a purely descriptive investigation, because of the non-axiomatizability of the domain of pure lived experiences. In this manner, phenomenology goes beyond the mere reduction of all scientific realities to a pure given, it also constitutes or constructs all scientific realities from it, although in a non logical sense of the term.
Husserl’s transcendentalism raises many questions that are clearly impossible to discuss here. One of them is however inescapable and needs to be answered, if only quickly, in order to make a confrontation with Carnap possible. How can phenomenology intend to constitute a reality that it must start by reducing ? This probably is the most challenging difficulty facing the Husserlian project. In the study mentioned above, Hintikka proposes to solve it by considering hyletic data not only as the given, but also as an entity common to the phenomenological domain and to all others. I believe that Hintikka’s interpretation is also mistaken in this regard, and that Husserlian phenomenology cannot make a step out of what is given in immanent intuition. Accordingly, it can only study the constitution of the phenomenon of transcendent reality, and not of transcendent reality itself. In the case of a perceived tree, for instance, it can only tell us how what Husserl calls in 1913 the noema of the tree is constituted, and not how the tree which actually burns when set afire is constituted.

52. Phenomenology as a possible basis for construction theory:

It is now possible to further specify the differences separating the Husserlrian and the Carnapian ways of reducing scientific reality to the given, as well as of constructing it from the given, beyond their obvious divergence about the relevance of logic to these two tasks.
These further differences are in fact numerous, and they confirm that the 1928 Carnapian idea of transforming scientific knowledge into a unique theoretical investigation of the given is fundamentally absent from Husserl’s thought, even at the phenomenological level, and even if a “mathesis of pure lived experiences” were indeed possible.
In the first place, the transcendental reduction to the given and the construction of scientific reality from the given are two different operations in Husserl, while they are one and the same in Carnap. Consequently, their relation with Carnap’s conception of the reduction to the given should be examined separately.
As previously underlined, the transcendental reduction resembles Carnap’s reduction in that it consists in transforming scientific reality into something given (reduced phenomena). However, one difference with Carnap is that it is, partially but fundamentally, a transformation of something already given (in non immanent intuition) into something given (purely so). For instance, it consists in part in reducing an observed physical reality - such as a tree - into the noema of that reality - such as the noema of a tree -, which is itself the object of an immanent intuition. Much more importantly, however, transcendental reduction does not really lead to the elimination of the reality that it reduces. On the one hand, it is just a suspension of the belief in the reality of the objects of science and not a negation of it. On the other hand, its goal is not to deny their reality, but on the contrary, to consolidate it, to make it legitimate by clarifying how these objects can possibly be given to a subject in an intuition. Husserl’s fundamental motive for going phenomenological, so to speak, is not to put into question the power of intuition, but to eliminate the rational imperfections surrounding its “naïve” use. Far from aiming at ontological economy, the ultimate goal of transcendental reduction is ontological wealth. Transcendental reduction does eliminate scientific reality, but only in a temporary manner and in a way that ends up making its diversity more irreducible. To put it in other words still, ‘going back’ to the pure lived experiences revealed in immanent intuition is the safest way of not having to give up on the multifaceted realm of being laid bare by transcendent intuitions. 
This fundamental difference in perspective pops up again when confronting Husserlian constitution with Carnapian construction. In fact, Husserlian constitution is closer to Carnapian construction than Husserlian reduction is to Carnapian reduction. In both cases, the basic idea is to obtain scientific reality on the basis of the given. However, the two goals being pursued are opposite: Husserlian constitution theory seeks to show how the pure lived experiences somehow create an entity ontologically different from themselves, while Carnapian construction theory seeks to show how an apparently ontological difference is no more than a logical one.
The fundamental difference of perspective that sets radically apart the phenomenological reduction and construction from their unique Carnapian counterpart would remain even if Husserl could accept the legitimacy of a mathesis of pure lived experiences. One reason for this is again the non-reductionist nature of logical construction for Husserl. It implies that, had Husserl for instance taken the concepts of hyletic data and noesis as basic elements of such a mathesis, he would have in no way concluded that the noema of a physical thing is no more than a logical arrangement of these elements (let alone the physical thing itself). Another reason, however, is that phenomenology and constitution theory address different questions in spite of their common foundational goal,  and this difference in questioning would still separate a Husserlian mathesis of pure lived experiences and the constructional system of the Aufbau. The object of phenomenology, as Husserl sees it, is to analyze processes of constitution, especially cognitive processes, on the basis of immanent intuition. As such, it corresponds - in part - fairly well to a theory of what Carnap calls the epistemic order. As a matter of fact, this is also how Carnap partially refers to it, as previously indicated. Even if Husserl could put this theory in mathematical form, its goal would still be to understand how objects are produced, and not how to eliminate them.
From this last remark, it follows that the only way in which Husserlian phenomenology could possibly converge with construction theory is in fact by providing it with a theory of what is actually given, in the sense of being epistemically primary, and more generally a theory of the epistemic order. Carnap is right when he occasionally establishes this sort of connection. But he is wrong when he pretends to go further and claim that his epistemic constructional system shares the same goal as Husserlian phenomenology. Even if he does in fact take the pure-lived experiences as a basis for his system – which remains a disputable matter not be explored again here –, his foundational project departs radically from Husserl’s one.

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