146 The Inconceivable as a Test of Truth. [March, 
philosophy at all. Kant saw that Locke had totally failed, 
as all men must fail, in the attempt to trace all our ideas to 
experience. He admitted the existence of a priori ideas or 
principles of mind, independent of all experience. The ad- 
mission of one such idea, on principle, is of course the anni- 
hilation of the empiric system. Kant taught that the 
phenomena of experience, meeting their a priori principles 
(which might as well be called innate), formed our knowledge, 
which was, therefore, the joint production of the Ego and the 
Non-Ego. Locke had compared the mind before experience 
to a sheet of blank paper. According to Kant’s view it might 
be compared to the glass of the photographer, on which the 
picture is the joint work of the sun’s rays and the prepara- 
tion of silver. It may be worth observing that in this last 
case the outlines are true to external objects, while the 
colouring is false. Now whatever title we may give to these 
a priori ideas — primary, innate, connate, or necessary— the 
acknowledgment of their existence is fatal to the theory that 
all our knowledge is based on experience. Kant acknow- 
ledged their existence, and thus opened at least a chink 
through which Descartes might peep and see how much 
had been really added to mental science since his time. 
But if our knowledge be not wholly founded on experience 
it may still (if it deserves the name) be founded on experi- 
ence and our nature, and so be truly subjective. Whether it 
is so is the question before us. If we can know anything 
with the certainty that it ever was and ever must be true, 
irrespective of our existence or the aCtual existence of any 
given beings, then so much of our knowledge, be it never so 
little, is necessary truth — not subjective, but objective. If, 
on the other hand, there be no truth so certain but that, in a 
new sphere, or with new enlightenment, we might find it to 
have been an illusion, then all that we have by way of know- 
ledge is subjective and possibly illusory. It cannot be 
called subjective because it is in us unless it also appear 
that it is of us. Are there then any Necessary Truths ? Dr. 
Whewell’s definition of necessary truths will suffice for my 
purpose. “ Necessary truths are those in which we not only 
learn that the proposition is true, but see that it must be 
true, in which the negative is not only false but impossible, 
in which we cannot, even by an effort of imagination, or in 
a supposition, conceive the reverse of what is asserted.” 
Here, the inconceivable is clearly admitted to be the test of 
the presence of a necessary truth, independent of ourselves. 
If then there be any proposition the contradictory of which 
is inconceivable, that proposition is true, and as part of our 
