Kant’a Synthetic A Priori
Kant's notion of synthesis lies at the center of his philosophy, and of his purported overhaul of classical metaphysics, as well as of Hume’s skepticism and empiricism. He conceived of his project as being a natural extension of the Copernican Revolution in speculative thought, which would place philosophy in the ‘secure path of the sciences’, in continuity with the ideal set by the Enlightenment. He characterized his project in the first Critique on general terms as follows:
“Up to now it has been assumed that all our cognition must conform to the objects; but all attempts to find out something about them a priori through concepts that would extend our cognition have, on this pre-supposition, come to nothing. Hence let us once try whether we do not get further with the problem of metaphysics by assuming that the objects must conform to our cognition, which would agree better with the requested possibility of an a priori cognition of them, which is to establish something about objects before they are given to us. This would be just like the first thought of Copernicus, who, when he did not make good progress in the explanation of the celestial motions if he assumed that the entire celestial host revolves around the observer, tried to see if it might not have greater success if he made the observer revolve and left the stars at rest” (Preface to Critique of Pure Reason B/XVI)
The basic idea is the following one: Kant accepts Hume's indictment against Cartesian rationalism in saying that knowledge is anchored in experience. This means that we have no transparent access to the contents of the world as it is 'in itself', i.e. classical metaphysics is nothing but naive realism.
However, he rejects Hume's skepticism about causality by claiming that empirical knowledge is constituted by a priori subjective faculties. As such, experience is not given to things-in-themselves (noumena), but to how things appear to us through these faculties (phenomena), i.e. knowledge is inherently mediated and so because of that it is representational. The class of the noumenal, however, must be distinguished from the category of object: the latter are functions of the synthesis given to the subject, while the former are the mere limiting concept of a being separable from the way it is given to us through perception in sensibility (CPR, 270-274). This is the sense in saying that noumenal reality is a negative concept. We can define Kant’s basic ontological position thus according to what the philosopher Quentin Meillassoux has called ‘correlationism’: the thesis that we have no access to being-in-itself, but only to the relation between being and the subject. In its ‘weak’ version, which Meillassoux attributes to Kant, the in-itself is not given, but is thinkable (After Finitude, Pgs. 23-27). This is decidedly different from the Absolute Idealist who claims the in-itself is identical to the for-itself of phenomenal thought (as we will see in for example, the case of Hegel).
Further, since causality is for Kant now said to necessarily derive not from things-in-themselves, but from the phenomena of experience, Kant argues that we can gain certain knowledge of causal necessity about objects, given that we adequately clarify how the subject comes to constitute experience as a result of his own faculties. This is the basic impetus guiding the idea of synthesis: it concerns elucidating those necessary or a priori features which articulate the content of experience into knowledge. Thus synthesis is for Kant an operation which involves both a) affects received passively by the subject in order to form objects, and b) a capacity for actively applying categorical judgments about these objects to discern concrete features which determine the objective content.
This means that every occasion of knowledge implies synthesis, but it is through the critical enquiry into the principles of knowledge that we understand the a priori features of synthesis, and the faculties they involve. Correspondingly, if knowledge is to be saved from Hume, it is because we have access to the structure of reason, and thus to the forms of synthesis that articulate experience.
This critical enquiry into pure reason must seek an answer to the question 'How are a priori synthetic judgments possible?'. This kind of knowledge is for Kant tantamount to judgments about that which simultaneously gives form to the content of experience (and thus synthetic), and yet which is necessarily prior to all actual contingent experience.
It is these kind of judgments which clarify how the subject organizes the content of experience, and so clarifies the features of those phenomena given to us, i.e. the synthetic a priori is ontological knowledge (Ontologia is Metaphysica Generalis, CPR
845f, B873f, A 247, B 303). Each occasion of experience is thus already determined by this (a priori) synthesis which is the act of the transcendental subject.
"Knowledge which brings forth the quiddity of the being, i.e. knowledge which unveils the being itself, Kant calls "synthetic". Thus the question concerning the possibility of ontological knowledge becomes the problem of the essence of a priori synthetic judgments" (Heidegger, KPM, Page 9)
Unlike analytic a priori concepts which concern merely conceptual determinations (matters 'of definition'), the synthetic a priori determines/specifies the content given to experience. It is not therefore abstracted from experience, but applies to it in every case as a matter of necessity. The faculty conformed by a priori principles is what Kant calls 'pure reason', and the enquiry into them is thus the object of the first Critique. Correspondingly, the enquiry into these principles is titled transcendental, insofar as it deals with how the act of the subject constitutes the content it passive receives in affection:
"I entitle all knowledge transcendental that is occupied in general not so much with objects as with the kind of knowledge we have of objects, insofar as this is possible a priori." (CPR, B25)
“Transcendental knowledge enquires not into just actual experience, like empiricists purport, but more generally into possible experience. Thus the principles of pure reason Kant also calls 'conditions of possibility' of all knowledge; it is a matter of "transcendental truth, which precedes all empirical truth and makes it possible." (CPR, a 146, B185).
This enquiry is the most difficult for Kant since "...nothing yet lies at the ground as given except for reason itself, and thus seeks to develop knowledge from its original seeds without seeking the support of any fact." (Prolegomena zu einer jeden kunftingen Metaphysik, $4, Werke, IV, Pg. 23). However, if all objective knowledge is synthetic then the critique must enquire into what exactly is being synthesized. This means that transcendental enquiry concerns just as much the affects, or the general ways in which things are given to us in sensibility, as well as the fundamental operations endowed to the content of sensibility by thinking in the understanding.
- The former enquiry is tethered to what Kant calls the 'Transcendental Aesthetic', which concerns sensibility. This concerns the way in which we receive the matter of experience.
- The latter enquiry is tethered to what Kant calls the 'Transcendental Analytic', which concerns understanding. This concerns the way in which we create or in-form data through concepts in thought.
We should mention in passing that it is because the transcendental subject needs thinking to supplement the content given to intuition and organize it that Kant can say that the subject is essentially finite. The pathos of finitude, which extends all the way into the 20th Century's obsession with the limits of our knowledge, is doubtlessly anchored and prefigured in Kant's basic thought that we only ever experience phenomenal entities, whose constitution is synthetic insofar as we are subject to receptivity, and need the contribution of the understanding to get 'objects'. Kant was thus, as Alain Badiou remarks, 'without doubt the creator in philosophy of the notion of the object', i.e. the object as something which stands-against a subject, and which is not himself, thus pointing to his limits (that which ob-jects to it). An infinite being, on the other hand would produce the being at the same time it intuits it: thus not needing thinking to organize the content of experience, since it would directly form the being-itself (the noumena) as it thinks it. Heidegger puts it nicely:
"The question concerning the possibility of a priori synthesis narrows down to this: how can a finite creature, which as such is delivered over to beings and is directed by the taking-in-stride of these same beings, know. intuit prior to all instances of taking the being-in-stride, without being its "creator"? (KPM: Pg 30)
Object, finitude, phenomena, synthesis, sensibility and thinking are thus all to be thought together as constitutive of the act of the transcendental subject.
THE TRANSCENDENTAL AESTHETIC: PURE FORMS OF INTUITION
With respect to the Aesthetic, we have already hinted towards its link to perception (aesthesis means perception in Greek). As we indicated, this part of the Critique concerns the enquiry into the faculty of sensibility. Although this faculty is fundamentally receptive insofar as it concerns data given to the subject, its content is already structured in a pre-conceptual manner. Kant clarifies that all active thinking organizes the content received by our sensibility, which is in other words what we passively intuit. However, since intuition is already given-to the subject, it is already conditioned or ‘formed’ by it, irrespective of the concrete contribution of the understanding (which we will review next).
Therefore, the most general features of this receptive capacity are at the same time the most general conditions of possibility for any thought to synthesize sense-data into objective experience. These conditions of possibility Kant calls the 'pure forms of intuition': space and time. These already constitute representations insofar as they are already given to the subject, mediated by our finite sensibility, as we indicated above.
It is important to note that these two forms are given in a unified and thus articulated way. Kant writes about space that "Space is represented as an infinite given magnitude" (A 25, B 39). This means that space (just like time) is not an empirical perception, or an object which gives itself within experience among others, discernible through concepts in judgment. Rather, space and time are the general forms or conditions under which any object of experience must be first given to the subject, logically prior to any act of constitution by the understanding. To say space is infinite in this regard simply means to say it does not correspond thus to any empirically given or specific magnitude, all of which are necessarily finite in experience. It is a 'unified whole', an original and 'pure representing' (A32, B48). But what is intuited is by itself not yet an determined object, even if it provides the content for such a determination. in the pure transcendental object Space constitutes in this way the ‘outer sense’ of synthetic activity.
Time is likewise a pure form, which organizes succession of given data to our minds. It is "the form of inner sense, i.e. of the intuiting of ourselves and our inner state...it has nothing to do with shape or position... Time is the formal a priori condition of all appearances whatsoever" (A33, B49). All appearances/phenomena must happen in time to subsist even as space, i.e. there is only something present insofar as it is present in time; and the same for the past and the future. Thus time has something of a logical precedence over space for Kant. Together, time and space form the pure forms of intuition.
THE TRANSCENDENTAL ANALYTIC: THE PURE CONCEPTS OF THE UNDERSTANDING
However, as we mentioned, time-space do not by themselves provide knowledge of any-thing; it has no objective content still. The pure transcendental object is undetermined, and a merely logical pole at the other end of the transcendental subject, but not yet robust. For objectivity to emerge, and thus the specificity of experience, Kant needs the active agency of thought which provides what he calls the 'pure concepts of the understanding', which are basically the basic ways in which the subject synthesizes of intuition-understanding in actual experience. As opposed to the pure forms of intuition, the analytic concerns the pure concepts of the understanding, or what Kant will come to call the 'categories' of the understanding.
These constitute the basic capacity of judgment, that is to say, the way in which we specify an object X to be such-and-such (A80). Kant thus says famously that "the conditions of the possibility of experience in general are likewise conditions of the possibility of the objects of experience." (A 158) Possible experience is unified in the dyad of intuition-understanding, forms and categories, sensibility and thinking.
Kant describes the categories as 'functions of thought', which have objects as their outputs. They thus relate to all objects generally. For Kant these categorical determinations are essentially twelve, each corresponding to a possible judgment about an object, which we now list schematically:
The Table of Categories / Judgments (A 71)
Reality / Affirmative
Inherence-Subsistence / Categorical
Plurality / Particular
Negation / Negative
Existence / Assertoric
Totality / Singular
Limitation / Infinite
Necessity / Apodictic
Having laid these out, we can understand the crucial distinction between analytic and synthetic judgments. All judgments have a subject-predicate structure, but whereas in analytic judgments the predicate does not add anything to the subject (all bachelors are unmarried), in synthetic judgments they do (My Budweiser is flat). Synthetic a priori judgments are thus simply those judgments which predicate of the object content specified by the categories, i.e. all objects have a cause, no event has a cause... It is interesting that for Kant the statements of science and pure mathematics are actually synthetic a priori. The classical example he provides is that of the simple sum 7+5 = 12. According to Kant, the concept 12 is not intrinsic to 7 or 5, one is said to ‘synthesize’ these by analogy to occasions of perception (one sees one’s fingers…). Of course this conception did not pass the test of time; Peano’s axiomatization of arithmetic shows it is perfectly possible to think of these statements as analytic; while Quine on the other hand launches an attack and questions whether there are any analytic judgments against Kant’s primitive taxonomy (see his Two Dogmas of Empiricism).
In a certain way, Kant's categories are continuous with the architectonic conception of Aristotle, except he inflects these determinations into the subject rather than locating them within the sphere of objects. Thus subsistence is not a property we know of things in themselves but is phenomenal: "In all change of appearances substance is permanent. This permanence is, however, simply the mode in which we represent to ourselves the existence of things (in the phenomenon)". As can be expected, the particular layout of the table of categories, as well as the –architectonic view- of the subject in principle, became the source for posterior attacks from other philosophers.
It is important to note however, that Kant needs both poles for the synthetic a priori to work. Without the understanding, the pure forms of intuition are void of objective specificity. The pure transcendental object stipulated by Kant would thus remain vacuous and helplessly general, one of which we know nothing in its emptiness: "This [transcendental object] cannot be entitled the noumenon; for I know nothing of what it is in itself, and have no concept of it save as merely the object of a sensible intuition in general" (CPR, A 253). Zizek here is illuminating:
"Transcendental object, that is, the completely indeterminate thought of something in general," has the function of conferring "upon all our empirical concepts in general relation to an object, that is, objective validity" ( CPR, A 109 )... Transcendental object is the form of the object in general by means of a reference to which a priori categories synthesize the multitude of sensible intuitions into the representation of a unified object: it marks the point at which the general form of every possible object reverts to the empty representation of the "object in general." (TWN, Pg. 36)
However, without intuition, we cannot know what a pure concept ever applies to, and thus we cannot have objective knowledge either:
“When this condition (of sensible intuition) has been omitted from the pure category, it can contain nothing but the logical function for bringing the manifold together under a concept. By means of this function or form of the concept, thus taken by itself, we cannot in any way know and distinguish what object comes under it, since we have abstracted from the sensible condition through which alone objects can come under it"
Kant neatly distributes the act of the subject across these two faculties (CPR 131-136):
1) We require the forms of intuition for the apprehension of sense data, its sequential-temporal ordering,
2) We require the categories of understanding for the recognition of the object under the concept.
However, there is an additionally intermediary ‘faculty’ or power, which is that of the imagination, which reproduces representations and produces combinations of the same (which Kant calls schemas, and which amount to procedural rules obtained from the synthesis of the imagination and time). This ambiguous role of the power of the imagination, somewhere in-between sensibility and the understanding opened the gulf for a series of speculative knots and quarrels with the tradition, of which famously Heidegger made the most of in his Kant and the Problem of Metaphysics (1928).
SOME CONSIDERATIONS ABOUT THE TRANSCENDENTAL SUBJECT
- It is interesting to note that Kant's transcendental subject introduces a split in the traditional conceptions of subjectivity, including the Cartesian subject. This is because the split between the noumenon/phenomenon goes all the way to the subject, i.e. there is a split between the logical subject which accompanies every 'I think', and the empirical subject or 'person' which can be identified with a substance. This is analogous to the pure transcendental object we discussed earlier to the actual object of synthetic experience.
This is an important point, since one may ask: what exactly holds the variety of objective syntheses together? This transcendental subject of experience, which logically unifies experience, enacts by Kant what he calls 'pure unity of apperception':
"There is one single experience in which all perceptions are represented as in thoroughgoing and orderly connection, just as there is only one space and one time in which all modes of appearance and all relations of being or not-being occur. When we speak of different experiences we can refer only to the various perceptions all of which, as such, belong to one and the same general experience. This thoroughgoing synthetic unity of perceptions is indeed the form of experience, it is nothing else than the synthetic unity of appearances in accordance to concepts... The unity of apperception is thus the transcendental ground of the necessary conformity to law of all appearances in one experience" (1929, A111-A127)
It is the synthetic unity of apperception which provides the basis for a universal cognitive experience. Pure apperception is the 'wellspring' of the synthetic a priori which constitutes the unifying function of the purely logical subject. The unity of apperception guarantees that experience is always of the same subject, no matter the contingent experiences. The subject is thus never, like in Descartes sense, one more substance among others (the hypostasized res cogitans in the chain of being); but it is this pure and empty formalizing agency of unifying synthesis in apperception: morphe - “form ‘informs’ matter”). It thus bridges the empty logical necessity of the analytic a priori, with the contentful empirical contingency of the synthetic a posteriori. This makes Habib’s reading, for example, of the forms of intuition as being ‘in the mind’ problematic (Pg. 363); the transcendental subject is certainly not the substantial mind indicated by the Cartesian cogito, and its unity is merely formal. It thus contains no properties; its synthesizing function is transcendental insofar as the categories are purely logical, i.e. nothing is strictu sensu in the transcendental subject.
Zizek has remarked, in his Lacanian reading of Kant, that it is precisely this gap between the logical subject of the 'I think' and the empirical self that becomes crucial in understanding Kant's sublation of Descartes. The former is strictly speaking not even an appearance, since it is never intuited, i.e. it is without content. But it is also not noumenal, since it is purely formal and empty; so if were to appear it could be lacking nothing: it would nullify the gap between noumena and phenomena constitutive of finite transcendence: "In the synthetic original unity of apperception, I am conscious of myself, not as I appear to myself, nor as I am in myself, but only that I am" (CPR, B 157)
The following passage clarifies this relationship:
“This gap which separates the empirical I's self-experience from the I of transcendental apperception coincides with the distinction between existence qua experiential reality and existence qua logical construction, the status of Kant's I of transcendental apperception is that of a necessary and simultaneously impossible logical construction ("impossible" in the precise sense that its notion can never be filled out with intuited experiential reality)" (Zizek, ibid)