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{30} See Critique of Pure Reason, Von den Paralogismen der reinen
Vernunft.
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§ 46. People have long since observed, that in all substances the
proper subject, that which remains after all the accidents (as
predicates) are abstracted, consequently that which forms the
substance of things remains unknown, and various complaints have been
made concerning these limits to our knowledge. But it will be well to
consider that the human understanding is not to be blamed for its
inability to know the substance of things, that is, to determine it by
itself, but rather for requiring to cognise it which is a mere idea
definitely as though it were a given object. Pure reason requires us
to seek for every predicate of a thing its proper subject, and for
this subject, which is itself necessarily nothing but a predicate, its
subject, and so on indefinitely (or as far as we can reach). But hence
it follows, that we must not hold anything, at which we can arrive, to
be an ultimate subject, and that substance itself never can be thought
by our understanding, however deep we may penetrate, even if all
nature were unveiled to us. For the specific nature of our
understanding consists in thinking everything discursively, that is,
representing it by concepts, and so by mere predicates, to which
therefore the absolute subject must always be wanting. Hence all the
real properties, by which we cognise bodies, are mere accidents, not
excepting impenetrability, which we can only represent to ourselves as
the effect of a power of which the subject is unknown to us.
Now we appear to have this substance in the consciousness of ourselves
(in the thinking subject), and indeed in an immediate intuition; for
all the predicates of an internal sense refer to the ego, as a
subject, and I cannot conceive myself as the predicate of any other
subject. Hence completeness in the reference of the given concepts as
predicates to a subject—not merely an idea, but an object—that is,
the absolute subject itself, seems to be given in experience. But this
expectation is disappointed. For the ego is not a concept,{31} but only
the indication of the object of the internal sense, so far as we
cognise it by no further predicate. Consequently it cannot be in
itself a predicate of any other thing; but just as little can it be a
determinate concept of an absolute subject, but is, as in all other
cases, only the reference of the internal phenomena to their unknown
subject. Yet this idea (which serves very well, as a regulative
principle, totally to destroy all materialistic explanations of the
internal phenomena of the soul) occasions by a very natural
misunderstanding a very specious argument, which, from this supposed
cognition of the substance of our thinking being, infers its nature,
so far as the knowledge of it falls quite without the complex of
experience.
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{31} Were the representation of the apperception (the Ego) a concept, by
which anything could be thought, it could be used as a predicate of
other things or contain predicates in itself. But it is nothing more
than the feeling of an existence without the least definite conception
and is only the representation of that to which all thinking stands in
relation (relatione accidentis).
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§ 47. But though we may call this thinking self (the soul) substance,
as being the ultimate subject of thinking which cannot be further
represented as the predicate of another thing; it remains quite empty
and without significance, if permanence—the quality which renders
the concept of substances in experience fruitful—cannot be proved of
it.
But permanence can never be proved of the concept of a substance, as a
thing in itself, but for the purposes of experience only. This is
sufficiently shown by the first Analogy of Experience,{32} and who ever
will not yield to this proof may try for himself whether he can
succeed in proving, from the concept of a subject which does not exist
itself as the predicate of another thing, that its existence is
thoroughly permanent, and that it cannot either in itself or by any
natural cause originate or be annihilated. These synthetical a priori
propositions can never be proved in themselves, but only in reference
to things as objects of possible experience.
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{32} Cf. Critique, Von den Analogien der Erfahrung.
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§ 48. If therefore from the concept of the soul as a substance, we
would infer its permanence, this can hold good as regards possible
experience only, not [of the soul] as a thing in itself and beyond all
possible experience. But life is the subjective condition of all our
possible experience, consequently we can only infer the permanence of
the soul in life; for the death of man is the end of all experience
which concerns the soul as an object of experience, except the
contrary be proved, which is the very question in hand. The permanence
of the soul can therefore only be proved (and no one cares for that)
during the life of man, but not, as we desire to do, after death; and
for this general reason, that the concept of substance, so far as it
is to be considered necessarily combined with the concept of
permanence, can be so combined only according to the principles of
possible experience, and therefore for the purposes of experience
only.{33}
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{33} It is indeed very remarkable how carelessly metaphysicians have
always passed over the principle of the permanence of substances
without ever attempting a proof of it; doubtless because they found
themselves abandoned by all proofs as soon as they began to deal with
the concept of substance. Common sense, which felt distinctly that
without this presupposition do union of perceptions in experience is
possible, supplied the want by a postulate. From experience itself it
never could derive such a principle, partly because substances cannot
be so traced in all their alterations and dissolutions, that the
matter can always be found undiminished, partly because the principle
contains necessity, which is always the sign of an a priori principle.
People then boldly applied this postulate to the concept of soul as a
substance, and concluded a necessary continuance of the soul after the
death of man (especially as the simplicity of this substance, which is
inferred from the indivisibility of consciousness, secured it from
destruction by dissolution). Had they found the genuine source of this
principle—a discovery which requires deeper researches than they
were ever inclined to make—they would have seen, that the law of the
permanence of substances has place for the purposes of experience
only, and hence can hold good of things so far as they are to be
cognised and conjoined with others in experience, but never
independently of all possible experience, and consequently cannot hold
good of the soul after death.
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§ 49. That there is something real without us which not only
corresponds, but must correspond, to our external perceptions, can
likewise be proved to be not a connexion of things in themselves, but
for the sake of experience. This means that there is something
empirical, i.e., some phenomenon in space without us, that admits of a
satisfactory proof, for we have nothing to do with other objects than
those which belong to possible experience; because objects which
cannot be given us in any experience, do not exist for us. Empirically
without me is that which appears in space, and space, together with
all the phenomena which it contains, belongs to the representations,
whose connexion according to laws of experience proves their objective
truth, just as the connexion of the phenomena of the internal sense
proves the actuality of my soul (as an object of the internal sense).
By means of external experience I am conscious of the actuality of
bodies, as external phenomena in space, in the same manner as by means
of the internal experience I am conscious of the existence of my soul
in time, but this soul is only cognised as an object of the internal
sense by phenomena that constitute an internal state, and of which the
essence in itself, which forms the basis of these phenomena, is
unknown. Cartesian idealism therefore does nothing but distinguish
external experience from dreaming; and the conformity to law (as a
criterion of its truth) of the former, from the irregularity and the
false illusion of the latter. In both it presupposes space and time as
conditions of the existence of objects, and it only inquires whether
the objects of the external senses, which we when awake put in space,
are as actually to be found in it, as the object of the internal
sense, the soul, is in time; that is, whether experience carries with
it sure criteria to distinguish it from imagination. This doubt,
however, may be easily disposed of, and we always do so in common life
by investigating the connexion of phenomena in both space and time
according to universal laws of experience, and we cannot doubt, when
the representation of external things throughout agrees therewith,
that they constitute truthful experience. Material idealism, in which
phenomena are considered as such only according to their connexion in
experience, may accordingly be very easily refuted; and it is just as
sure an experience, that bodies exist without us (in space), as that I
myself exist according to the representation of the internal sense (in
time): for the notion without us, only signifies existence in space.
However as the Ego in the proposition, "I am," means not only the
object of internal intuition (in time), but the subject of
consciousness, just as body means not only external intuition (in
space), but the thing-in-itself, which is the basis of this
phenomenon; [as this is the case] the question, whether bodies (as
phenomena of the external sense) exist as bodies apart from my
thoughts, may without any hesitation be denied in nature. But the
question, whether I myself as a phenomenon of the internal sense (the
soul according to empirical psychology) exist apart from my faculty of
representation in time, is an exactly similar inquiry, and must
likewise be answered in the negative. And in this manner everything,
when it is reduced to its true meaning, is decided and certain. The
formal (which I have also called transcendental) actually abolishes
the material, or Cartesian, idealism. For if space be nothing but a
form of my sensibility, it is as a representation in me just as actual
as I myself am, and nothing but the empirical truth of the
representations in it remains for consideration. But, if this is not
the case, if space and the phenomena in it are something existing
without us, then all the criteria of experience beyond our perception
can never prove the actuality of these objects without us.