to all possible questions of a certain class。 Thus scepticism is a
resting place for reason； in which it may reflect on its dogmatical
wanderings and gain some knowledge of the region in which it happens
to be； that it may pursue its way with greater certainty； but it
cannot be its permanent dwelling…place。 It must take up its abode only
in the region of plete certitude； whether this relates to the
cognition of objects themselves； or to the limits which bound all
our cognition。
Reason is not to be considered as an indefinitely extended plane； of
the bounds of which we have only a general knowledge； it ought
rather to be pared to a sphere； the radius of which may be found
from the curvature of its surface… that is； the nature of a priori
synthetical propositions… and； consequently； its circumference and
extent。 Beyond the sphere of experience there are no objects which
it can cognize； nay； even questions regarding such supposititious
objects relate only to the subjective principles of a plete
determination of the relations which exist between the
understanding…conceptions which lie within this sphere。
We are actually in possession of a priori synthetical cognitions； as
is proved by the existence of the principles of the understanding；
which anticipate experience。 If any one cannot prehend 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 bee 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 pletely 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 mon 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 pleteness 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 a