The only ones which do so are those, the truth of which is 
positively unthinkable. Others vary greatly in distinctness 
and adequacy ; but the fact that we habitually think and reason 
on them proves that they lie within the limits of rational 
inquiry. 
23. Again, as far as this question is concerned, to affirm that 
many of our certitudes are not the result of the experience of the 
individual, but of his remote ancestors, is to transfer thediffi- 
culty, but not to solve it. I ask, on what did the primary ex- 
perience of our remote ancestors rest? What gave it validity ? 
However small its results, it must have possessed some princi- 
ple, which rendered it possible. Let us suppose, for the sake 
of argument, that the affirmation, that things which are equal 
to the same thing, are equal to each other, is the result of a 
gradually accumulated experience, which, after repeated trans- 
missions, now exhibits itself in our minds in the form of an 
intuition. Does this account of it as the result of a transmitted 
experience give any account of the primary conception of 
equality ; or of the affirmation, that when two things are equal 
to the same thing they must be equal to one another? Does 
it inform us, how the power of comparison between two equal 
things originated ? The being w r ho could thus compare must have 
been separated from one who could not — not by a small interval, 
but by a wide and deep gulf. Will the tracing it through myriads 
of years help us to dispense with a commencement of the con- 
ception ? The only possible account of the matter is, that there 
must exist some fundamental principle in the mind, which 
enables us to see that it must be objectively valid for all time 
and all space. I do not deny that experience may be the 
medium through which such a power may be called from a 
dormant into an active state. Yet this does not affect the proof 
that some truth must transcend experience. Were it not so, 
all universal affirmations would be impossible. 
24. Further : some principle must exist in the mind, which 
is the foundation of its conviction that past events, when the 
conditions are the same, will repeat themselves in the future. 
Unless this be so, the affirmation of universal law, embracing 
alike the past, the present and the future, would be invalid. 
It is impossible that it can be given by experience alone. 
25. It is evident that every affirmation respecting the future 
must transcend experience ; for experience can be only of the 
present and the past. The future has not yet existed, and 
therefore experience of it is impossible. How, then, have we 
arrived at the belief that the future will be like the past? To 
put the question into a concrete form. How are we justified 
