Critique of Pure Reason

by Immanuel Kant

  If our knowledge of thinking beings in general, so far as it is derived from pure reason, were founded on more than the cogito, and if we made use at the same time of observations on the play of our thoughts and the natural laws of the thinking self, derived from them, we should have before us an empirical psychology, which would form a kind of physiology of the internal sense, and perhaps explain its manifestations, but would never help us to understand such properties as do not fall under any possible experience (as, for instance, simplicity), or to teach apodictically anything touching the nature of thinking beings in general. It would not therefore be a rational psychology.

  As the proposition I think (taken problematically) contains the form of every possible judgment of the understanding, and accompanies all categories as their vehicle, it must be clear that the conclusions to be drawn from it can only contain a transcendental use of the understanding, which declines all admixture of experience, and of the achievements of which, after what has been said before, we cannot form any very favourable anticipations. We shall therefore follow it, with a critical eye, through all the predicaments of pure psychology.2

  [The First Paralogism of Substantiality

  That the representation of which is the absolute subject of our judgments, and cannot be used therefore as the determination of any other thing, is the substance.

  I, as a thinking being, am the absolute subject of all my possible judgments, and this representation of myself can never be used as the predicate of any other thing.

  Therefore I, as a thinking being (Soul), am Substance.

  Criticism of the First Paralogism of Pure3 Psychology

  We showed in the analytical portion of transcendental logic, that pure categories, and among them that of substance, have in themselves no objective meaning, unless they rest on some intuition, and are applied to the manifold of such intuitions as functions of synthetical unity. Without this they are merely functions of a judgment without contents. I may say of everything, that it is a substance, so far as I distinguish it from what are mere predicates and determinations. Now in all our thinking the I is the subject, in which thoughts are inherent as determinations only; nor can that I ever be used as a determination of any other thing. Thus everybody is constrained to look upon himself as the substance, and on thinking as the accidents only of his being, and determinations of his state.

  But what use are we to make of such a concept of a substance? That I, as a thinking being, continue for myself, and naturally neither arise nor perish, is no legitimate deduction from it; and yet this conclusion would be the only advantage that could be gained from the concept of the substantiality of my own thinking subject, and, but for that, I could do very well without it.

  So far from being able to deduce these properties from the pure category of substance, we have on the contrary to observe the permanency of an object in our experience and then lay hold of this permanency, if we wish to apply to it the empirically useful concept of substance. In this case, however, we had no experience to lay hold of, but have only formed a deduction from the concept of the relation which all thinking has to the I, as the common subject to which it belongs. Nor should we, whatever we did, succeed by any certain observation in proving such permanency. For though the I exists in all thoughts, not the slightest intuition is connected with that representation, by which it might be distinguished from other objects of intuition. We may very well perceive therefore that this representation appears again and again in every act of thought, but not that it is a constant and permanent intuition, in which thoughts, as being changeable, come and go.

  Hence it follows that in the first syllogism of transcendental psychology reason imposes upon us an apparent knowledge only, by representing the constant logical subject of thought as the knowledge of the real subject in which that knowledge inheres. Of that subject, however, we have not and cannot have the slightest knowledge, because consciousness is that which alone changes representations into thoughts, and in which therefore, as the transcendental subject, all our perceptions must be found. Beside this logical meaning of the I, we have no knowledge of the subject in itself, which forms the substratum and foundation of it and of all our thoughts. In spite of this, the proposition that the soul is a substance may well be allowed to stand, if only we see that this concept cannot help us on in the least or teach us any of the ordinary conclusions of rationalising psychology, as, for instance, the everlasting continuance of the soul amid all changes and even in death, and that it therefore signifies a substance in idea only, and not in reality.

  The Second Paralogism of Simplicity

  Everything, the action of which can never be considered as the concurrence of several acting things, is simple.

  Now the Soul, or the thinking I, is such a thing:—

  Therefore, etc.

  Criticism of the Second Paralogism of Transcendental Psychology

  This is the strong (yet not invulnerable) syllogism among all dialectical syllogisms of pure psychology, not a mere sophism contrived by a dogmatist in order to impart a certain plausibility to his assertions, but a syllogism which seems able to stand the sharpest examination and the gravest doubts of the philosopher. It is this:—

  Every composite substance is an aggregate of many substances, and the action of something composite, or that which is inherent in it as such, is an aggregate of many actions or accidents distributed among many substances. An effect due to the concurrence of many acting substances is no doubt possible, if that effect is external only (as, for instance, the motion of a body is the combined motion of all its parts). The case is different however with thoughts, if considered as accidents belonging to a thinking being within. For suppose it is the composite which thinks, then every part of it would contain a part of the thought, and all together only the whole of it. This however is self-contradictory. For as representations, distributed among different beings (like the single words of a verse), never make a whole thought (a verse), it is impossible that a thought should be inherent in something composite, as such. Thought therefore is possible only in a substance which is not an aggregate of many, and therefore absolutely simple.4

  What is called the nervus probandi in this argument lies in the proposition that, in order to constitute a thought, the many representations must be comprehended under the absolute unity of the thinking subject. Nobody however can prove this proposition from concepts. For how would he undertake to do it? The proposition that a thought can only be the effect of the absolute unity of a thinking being, cannot be considered as analytical. For the unity of thought, consisting of many representations, is collective, and may, so far as mere concepts are concerned, refer to the collective unity of all co-operating substances (as the movement of a body is the compound movement of all its parts) quite as well as to the absolute unity of the subject. According to the rule of identity it would be impossible therefore to establish the necessity of the presupposition of a simple substance, the thought being composite. That, on the other hand, such a proposition might be established synthetically and entirely a priori from mere concepts, no one will venture to affirm who has once understood the grounds on which the possibility of synthetical propositions a priori rests, as explained by us before.

  It is likewise impossible, however, to derive this necessary unity of the subject, as the condition of the possibility of the unity of every thought, from experience. For experience never supplies any necessity of thought, much less the concept of absolute unity. Whence then do we take that proposition on which the whole psychological syllogism of reason rests?

  It is manifest that if we wish to represent to ourselves a thinking being, we must put ourselves in its place, and supplant as it were the object which has to be considered by our own subject (which never happens in any other kind of investigation). The reason why we postulate for every thought absolute unity of the subject is because otherwise we could not say of it, I think (the manifold in one representation). For although the whole of a thought ma
y be divided and distributed under many subjects, the subjective I can never thus be divided and distributed, and it is this I which we presuppose in every thought.

  As in the former paralogism therefore, so here also, the formal proposition of apperception, I think, remains the sole ground on which rational psychology ventures to undertake the extension of its knowledge. That proposition, however, is no experience, but only the form of apperception inherent in, and antecedent to, every experience, that is a purely subjective condition, having reference to a possible experience only, but by no means the condition of the possibility of the knowledge of objects, and by no means necessary to the concept of a thinking being in general; although it must be admitted that we cannot represent to ourselves another intelligent being without putting ourselves in its place with that formula of our consciousness.

  Nor is it true that the simplicity of my self (as a soul) is really deduced from the proposition, I think, for it is already involved in every thought itself. The proposition I am simple must be considered as the immediate expression of apperception, and the so-called syllogism of Cartesius, cogito, ergo sum, is in reality tautological, because cogito (sum cogitans) predicates reality immediately. I am simple means no more than that this representation of I does not contain the smallest trace of manifoldness, but is absolute (although merely logical) unity.

  Thus we see that the famous psychological argument is founded merely on the indivisible unity of a representation, which only determines the verb with reference to a person; and it is clear that the subject of inherence is designated transcendentally only by the I, which accompanies the thought, without our perceiving the smallest quality of it, in fact, without our knowing anything about it. It signifies a something in general (a transcendental subject) the representation of which must no doubt be simple, because nothing is determined in it, and nothing can be represented more simple than by the concept of a mere something. The simplicity however of the representation of a subject is not therefore a knowledge of the simplicity of the subject, because no account whatever is taken of its qualities when it is designated by the entirely empty expression I, an expression that can be applied to every thinking subject.

  So much is certain therefore that though I always represent by the I an absolute, but only logical, unity of the subject (simplicity), I never know thereby the real simplicity of my subject. We saw that the proposition, I am a substance, signified nothing but the mere category of which I must not make any use (empirically) in concreto. In the same manner, I may well say, I am a simple substance, that is, a substance the representation of which contains no synthesis of the manifold; but that concept, or that proposition also, teaches us nothing at all with reference to myself, as an object of experience, because the concept of substance itself is used as a function of synthesis only, without any intuition to rest on, and therefore without any object, valid with reference to the condition of our knowledge only, but not with reference to any object of it. We shall test the usefulness of this proposition by an experiment.

  Everybody must admit that the assertion of the simple nature of the soul can only be of any value in so far as it enables me to distinguish the soul from all matter, and thus to except it from that decay to which matter is at all times subject. It is for that use that our proposition is really intended, and it is therefore often expressed by, the soul is not corporeal. If then I can show that, although we allow to this cardinal proposition of rational psychology (as a mere judgment of reason from pure categories) all objective validity (everything that thinks is simple substance), we cannot make the least use of it, in order to establish the homogeneousness or non-homogeneousness of soul and matter, this will be the same as if I had relegated this supposed psychological truth to the field of mere ideas, without any real or objective use.

  We have irrefutably proved in the transcendental Æsthetic that bodies are mere phenomena of our external sense, not things by themselves. We are justified therefore in saying that our thinking subject is not a body, i.e. that, because it is represented by us as an object of the internal sense, it is, so far as it thinks, no object of our external senses, and no phenomenon in space. This means the same as that among external phenomena we can never have thinking beings as such, or ever see their thoughts, their consciousness, their desires, etc., externally. All this belongs to the internal sense. This argument seems indeed so natural and popular that even the commonest understanding has always been led to it, the distinction between souls and bodies being of very early date.

  But although extension, impermeability, cohesion, and motion, in fact everything that the external senses can give us, cannot be thoughts, feeling, inclination, and determination, or contain anything like them, being never objects of external intuition, it might be possible, nevertheless, that that something which forms the foundation of external phenomena, and which so affects our sense as to produce in it the representations of space, matter, form, etc., if considered as a noumenon (or better as a transcendental object) might be, at the same time, the subject of thinking, although by the manner in which it affects our external sense it produces in us no intuitions of representations, will, etc., but only of space and its determinations. This something, however, is not ex tended, not impermeable, not composite, because such predicates concern sensibility only and its intuition, whenever we are affected by these (to us otherwise unknown) objects. These expressions, however, do not give us any information what kind of object it is, but only that, if considered by itself, without reference to the external senses, it has no right to these predicates, peculiar to external appearance. The predicates of the internal sense, on the contrary, such as representation, thinking, etc., are by no means contradictory to it, so that really, even if we admit the simplicity of its nature, the human soul is by no means sufficiently distinguished from matter, so far as its substratum is concerned, if (as it ought to be) matter is considered as a phenomenon only.

  If matter were a thing by itself, it would, as a composite being, be totally different from the soul, as a simple being. But what we call matter is an external phenomenon only, the substratum of which cannot possibly be known by any possible predicates. I can therefore very well suppose that that substratum is simple, although in the manner in which it affects our senses it produces in us the intuition of something extended, and therefore composite, so that the substance which, with reference to our external sense, possesses extension, might very well by itself possess thoughts which can be represented consciously by its own internal sense. In such wise the same thing which in one respect is called corporeal, would in another respect be at the same time a thinking being, of which though we cannot see its thoughts, we can yet see the signs of them phenomenally. Thus the expression that souls only (as a particular class of substances) think, would have to be dropt, and we should return to the common expression that men think, that is, that the same thing which, as an external phenomenon, is extended, is internally, by itself, a subject, not composite, but simple and intelligent.

  But without indulging in such hypotheses, we may make this general remark, that if I understand by soul a being by itself, the very question would be absurd, whether the soul be homogeneous or not with matter which is not a thing by itself, but only a class of representations within us; for so much at all events must be clear, that a thing by itself is of a different nature from the determinations which constitute its state only.

  If, on the contrary, we compare the thinking I, not with matter, but with that object of the intellect that forms the foundation of the external phenomena which we call matter, then it follows, as we know nothing whatever of the matter, that we have no right to say that the soul by itself is different from it in any respect.

  The simple consciousness is not therefore a knowledge of the simple nature of our subject, so that we might thus distinguish the soul from matter, as a composite being.

  If therefore, in the only case where that concept might be useful, namely, in comparing myself with objec
ts of external experience, it is impossible to determine the peculiar and distinguishing characteristics of its nature, what is the use, if we pretend to know that the thinking I, or the soul (a name for the transcendental object of the internal sense), is simple? Such a proposition admits of no application to any real object, and cannot therefore enlarge our knowledge in the least.

  Thus collapses the whole of rational psychology, with its fundamental support, and neither here nor elsewhere can we hope by means of mere concepts (still less through the mere subjective form of all our concepts, that is, through our consciousness) and without referring these concepts to a possible experience, to extend our knowledge, particularly as even the fundamental concept of a simple nature is such that it can never be met with in experience, so that no chance remains of arriving at it as a concept of objective validity.

  The Third Paralogism of Personality

  Whatever is conscious of the numerical identity of its own self at different times, is in so far a person.

  Now the Soul, etc.