here was no beginning, and continues in
a future to which there is no end.

[Sidenote: As to the criterion of truth--sense-delusions.]

(4.) Of the possibility of a criterion of truth. An absolute criterion
of truth must at once accredit itself, as well as other things. At a
very early period in philosophy the senses were detected as being
altogether untrustworthy. On numberless occasions, instead of
accrediting, they discredit themselves. A stick, having a spark of fire
at one end, gives rise to the appearance of a circle of light when it is
turned round quickly. The rainbow seems to be an actually existing arch
until the delusion is detected by our going to the place over which it
seems to rest. Nor is it alone as respects things for which there is an
exterior basis or foundation, such as the spark of fire in one of these
cases, and the drops of water in the other. Each of our organs of sense
can palm off delusions of the most purely fictitious kind. The eye may
present apparitions as distinct as the realities among which they place
themselves; the ear may annoy us with the continual repetition of a
murmuring sound, or parts of a musical strain, or articulate voices,
though we well know that it is all a delusion; and in like manner, in
their proper way, in times of health, and especially in those of
sickness, will the other senses of taste, and touch, and smell practise
upon us their deceptions.

This being the case, how shall we know that any information derived from
such unfaithful sources is true? Pythagoras rendered a great service in
telling us to remember that we have within ourselves a means of
detecting fallacy and demonstrating truth. What is it that assures us of
the unreality of the fiery circle, the rainbow, the spectre, the voices,
the crawling of insects upon the skin? Is it not reason? To reason may
we not then trust?

[Sidenote: Uncertainties in philosophizing.]

With such facts before us, what a crowd of inquiries at once presses
upon our attention--inquiries which even in modern times have occupied
the thoughts of the greatest metaphysicians. Shall we begin our studies
by examining sensations or by examining ideas? Shall we say with
Descartes that all clear ideas are true? Shall we inquire with Spinoza
whether we have any ideas independent of experience? With Hobbes, shall
we say that all our thoughts are begotten by and are the representatives
of objects exterior to us; that our conceptions ari