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is proved by the existence of the principles of the understanding,

which anticipate experience. If any one cannot comprehend the

possibility of these principles, he may have some reason to doubt

whether they are really a priori; but he cannot on this account

declare them to be impossible, and affirm the nullity of the steps

which reason may have taken under their guidance. He can only say:

If we perceived their origin and their authenticity, we should be able

to determine the extent and limits of reason; but, till we can do

this, all propositions regarding the latter are mere random

assertions. In this view, the doubt respecting all dogmatical

philosophy, which proceeds without the guidance of criticism, is

well grounded; but we cannot therefore deny to reason the ability to

construct a sound philosophy, when the way has been prepared by a

thorough critical investigation. All the conceptions produced, and all

the questions raised, by pure reason, do not lie in the sphere of

experience, but in that of reason itself, and hence they must be

solved, and shown to be either valid or inadmissible, by that faculty.

We have no right to decline the solution of such problems, on the

ground that the solution can be discovered only from the nature of

things, and under pretence of the limitation of human faculties, for

reason is the sole creator of all these ideas, and is therefore

bound either to establish their validity or to expose their illusory

nature.

The polemic of scepticism is properly directed against the

dogmatist, who erects a system of philosophy without having examined

the fundamental objective principles on which it is based, for the

purpose of evidencing the futility of his designs, and thus bringing

him to a knowledge of his own powers. But, in itself, scepticism

does not give us any certain information in regard to the bounds of

our knowledge. All unsuccessful dogmatical attempts of reason are

facia, which it is always useful to submit to the censure of the

sceptic. But this cannot help us to any decision regarding the

expectations which reason cherishes of better success in future

endeavours; the investigations of scepticism cannot, therefore, settle

the dispute regarding the rights and powers of human reason.

Hume is perhaps the ablest and most ingenious of all sceptical

philosophers, and his writings have, undoubtedly, exerted the most

powerful influence in awakening reason to a thorough investigation

into its own powers. It will, therefore, well repay our labours to

consider for a little the course of reasoning which he followed and

the errors into which he strayed, although setting out on the path

of truth and certitude.

Hume was probably aware, although he never clearly developed the

notion, that we proceed in judgements of a certain class beyond our

conception if the object. I have termed this kind of judgement

synthetical. As regard the manner in which I pass beyond my conception

by the aid of experience, no doubts can be entertained. Experience

is itself a synthesis of perceptions; and it employs perceptions to

increment the conception, which I obtain by means of another

perception. But we feel persuaded that we are able to proceed beyond a

conception, and to extend our cognition a priori. We attempt this in

two ways- either, through the pure understanding, in relation to

that which may become an object of experience, or, through pure

reason, in relation to such properties of things, or of the

existence of things, as can never be presented in any experience. This

sceptical philosopher did not distinguish these two kinds of

judgements, as he ought to have done, but regarded this augmentation

of conceptions, and, if we may so express ourselves, the spontaneous

generation of understanding and reason, independently of the

impregnation of experience, as altogether impossible. The so-called

a priori principles of these faculties he consequently held to be

invalid and imaginary, and regarded them as nothing but subjective

habits of thought originating in experience, and therefore purely

empirical and contingent rules, to which we attribute a spurious

necessity and universality. In support of this strange assertion, he

referred us to the generally acknowledged principle of the relation

between cause and effect. No faculty of the mind can conduct us from

the conception of a thing to the existence of something else; and

hence he believed he could infer that, without experience, we

possess no source from which we can augment a conception, and no

ground sufficient to justify us in framing a judgement that is to

extend our cognition a priori. That the light of the sun, which shines

upon a piece of wax, at the same time melts it, while it hardens clay,

no power of the understanding could infer from the conceptions which

we previously possessed of these substances; much less is there any

a priori law that could conduct us to such a conclusion, which

experience alone can certify. On the other hand, we have seen in our

discussion of transcendental logic, that, although we can never

proceed immediately beyond the content of the conception which is

given us, we can always cognize completely a priori- in relation,

however, to a third term, namely, possible experience- the law of

its connection with other things. For example, if I observe that a

piece of wax melts, I can cognize a priori that there must have been

something (the sun's heat) preceding, which this law; although,

without the aid of experience, I could not cognize a priori and in a

determinate manner either the cause from the effect, or the effect

from the cause. Hume was, therefore, wrong in inferring, from the

contingency of the determination according to law, the contingency

of the law itself; and the passing beyond the conception of a thing to

possible experience (which is an a priori proceeding, constituting the

objective reality of the conception), he confounded with our synthesis

of objects in actual experience, which is always, of course,

empirical. Thus, too, he regarded the principle of affinity, which has

its seat in the understanding and indicates a necessary connection, as

a mere rule of association, lying in the imitative faculty of

imagination, which can present only contingent, and not objective

connections.

The sceptical errors of this remarkably acute thinker arose

principally from a defect, which was common to him with the

dogmatists, namely, that he had never made a systematic review of

all the different kinds of a priori synthesis performed by the

understanding. Had he done so, he would have found, to take one

example among many, that the principle of permanence was of this

character, and that it, as well as the principle of causality,

anticipates experience. In this way he might have been able to

describe the determinate limits of the a priori operations of

understanding and reason. But he merely declared the understanding

to be limited, instead of showing what its limits were; he created a

general mistrust in the power of our faculties, without giving us

any determinate knowledge of the bounds of our necessary and

unavoidable ignorance; he examined and condemned some of the

principles of the understanding, without investigating all its

powers with the completeness necessary to criticism. He denies, with

truth, certain powers to the understanding, but he goes further, and

declares it to be utterly inadequate to the a priori extension of

knowledge, although he has not fully examined all the powers which

reside in the faculty; and thus the fate which always overtakes

scepticism meets him too. That is to say, his own declarations are

doubted, for his objections were based upon facta, which are

contingent, and not upon principles, which can alone demonstrate the

necessary invalidity of all dogmatical assertions.

As Hume makes no distinction between the well-grounded claims of the

understanding and the dialectical pretensions of reason, against

which, however, his attacks are mainly directed, reason does not

feel itself shut out from all attempts at the extension of a priori

cognition, and hence it refuses, in spite of a few checks in this or

that quarter, to relinquish such efforts. For one naturally arms

oneself to resist an attack, and becomes more obstinate in the resolve

to establish the claims he has advanced. But a complete review of

the powers of reason, and the conviction thence arising that we are in

possession of a limited field of action, while we must admit the

vanity of higher claims, puts an end to all doubt and dispute, and

induces reason to rest satisfied with the undisturbed possession of

its limited domain.

To the uncritical dogmatist, who has not surveyed the sphere of

his understanding, nor determined, in accordance with principles,

the limits of possible cognition, who, consequently, is ignorant of

his own powers, and believes he will discover them by the attempts

he makes in the field of cognition, these attacks of scepticism are

not only dangerous, but destructive. For if there is one proposition

in his chain of reasoning which be he cannot prove, or the fallacy

in which be cannot evolve in accordance with a principle, suspicion

falls on all his statements, however plausible they may appear.

And thus scepticism, the bane of dogmatical philosophy, conducts

us to a sound investigation into the understanding and the reason.

When we are thus far advanced, we need fear no further

attacks; for the limits of our domain are clearly marked out, and we

can make no claims nor become involved in any disputes regarding the

region that lies beyond these limits. Thus the sceptical procedure

in philosophy does not present any solution of the problems of reason,

but it forms an excellent exercise for its powers, awakening its

circumspection, and indicating the means whereby it may most fully

establish its claims to its legitimate possessions.

SECTION III. The Discipline of Pure Reason in Hypothesis.

This critique of reason has now taught us that all its efforts to

extend the bounds of knowledge, by means of pure speculation, are

utterly fruitless. So much the wider field, it may appear, lies open

to hypothesis; as, where we cannot know with certainty, we are at

liberty to make guesses and to form suppositions.

Imagination may be allowed, under the strict surveillance of reason,

to invent suppositions; but, these must be based on something that

is perfectly certain- and that is the possibility of the object. If we

are well assured upon this point, it is allowable to have recourse

to supposition in regard to the reality of the object; but this

supposition must, unless it is utterly groundless, be connected, as

its ground of explanation, with that which is really given and

absolutely certain. Such a supposition is termed a hypothesis.

It is beyond our power to form the least conception a priori of

the possibility of dynamical connection in phenomena; and the category

of the pure understanding will not enable us to ex. cogitate any

such connection, but merely helps us to understand it, when we meet

with it in experience. For this reason we cannot, in accordance with

the categories, imagine or invent any object or any property of an

object not given, or that may not be given in experience, and employ

it in a hypothesis; otherwise, we should be basing our chain of

reasoning upon mere chimerical fancies, and not upon conceptions of

things. Thus, we have no right to assume the existence of new

powers, not existing in nature- for example, an understanding with a

non-sensuous intuition, a force of attraction without contact, or some

new kind of substances occupying space, and yet without the property

of impenetrability- and, consequently, we cannot assume that there

is any other kind of community among substances than that observable

in experience, any kind of presence than that in space, or any kind of

duration than that in time. In one word, the conditions of possible

experience are for reason the only conditions of the possibility of

things; reason cannot venture to form, independently of these

conditions, any conceptions of things, because such conceptions,

although not self-contradictory, are without object and without

application.

The conceptions of reason are, as we have already shown, mere ideas,

and do not relate to any object in any kind of experience. At the same

time, they do not indicate imaginary or possible objects. They are

purely problematical in their nature and, as aids to the heuristic

exercise of the faculties, form the basis of the regulative principles

for the systematic employment of the understanding in the field of

experience. If we leave this ground of experience, they become mere

fictions of thought, the possibility of which is quite indemonstrable;

and they cannot, consequently, be employed as hypotheses in the

explanation of real phenomena. It is quite admissible to cogitate

the soul as simple, for the purpose of enabling ourselves to employ

the idea of a perfect and necessary unity of all the faculties of

the mind as the principle of all our inquiries into its internal

phenomena, although we cannot cognize this unity in concreto. But to

assume that the soul is a simple substance (a transcendental

conception) would be enouncing a proposition which is not only

indemonstrable- as many physical hypotheses are- but a proposition

which is purely arbitrary, and in the highest degree rash. The

simple is never presented in experience; and, if by substance is

here meant the permanent object of sensuous intuition, the possibility

of a simple phenomenon is perfectly inconceivable. Reason affords no

good grounds for admitting the existence of intelligible beings, or of

intelligible properties of sensuous things, although- as we have no

conception either of their possibility or of their impossibility- it

will always be out of our power to affirm dogmatically that they do

not exist. In the explanation of given phenomena, no other things

and no other grounds of explanation can be employed than those which