It may be said of David Hume that he initiated the attack on pure
reason. My own labours in the investigation of this subject were
occasioned by his sceptical teaching, for his assault made them
necessary. He argued that without experience it is impossible to know
the difference between one thing and another; that is, we can know _a
priori_, and, therefore, the notion of a cause is fictitious and
illusory, arising only from the habit of observing certain things
associated with each in succession of connections.
On such principles we can never come to any conclusion as to causes and
effects. We can never predict a consequence from any of the known
attributes of things. We can never say of any event that it must
_necessarily_ have followed from another; that is, that it must have had
an antecedent cause. And we could never lay down a rule derived even
from the greatest number of observations. Hence we must trust entirely
to blind chance, abolishing all reason, and such a surrender establishes
scepticism in an impregnable citadel.
Mathematics escaped Hume, because he considered that its propositions
were analytical, proceeding from one determination to another, by reason
of identity contained in each. But this is not really so, for, on the
contrary, they are synthetical, the results depending ultimately on the
assent of observers as witnesses to the universality of propositions. So
Hume's empiricism leads inevitably to scepticism even in this realm.
My investigations led me to the conclusion that the objects with which
we are familiar are by no means things in themselves, but are simply
phenomena, connected in a certain way with experience. So that without
contradiction they cannot be separated from that connection. Only by
that experience can they be recognised. I was able to prove the
objective reality of the concept of cause in regard to objects of
experience, and to demonstrate its origin from pure understanding,
without experimental or empirical sources.
Thus, I first destroyed the source of scepticism, and then the resulting
scepticism itself. And thus was subverted the thorough doubt as to
whatever theoretic reason claims to perceive, as well as the claim of
Hume that the concept of causality involved something absolutely
unthinkable.