e present.

But now, mark the difference. In our scientific analysis of popularly
known illusions, we had something by which to determine the illusory
character of the presentation or belief. We had a popularly or
scientifically accepted standard of certainty, by a reference to which
we might test the particular _soi-disant_ cognition. But in the case of
these fundamental beliefs we have no such criterion, except we adopt
some particular philosophic theory, say that of the associationist
himself. Hence this similarity in structure and origin cannot in itself
be said to amount to a proof of equality of logical or objective value.
Here again it must be remarked that origin, does not carry validity or
invalidity with it.[159]

We thus come back to our starting-point. While there are close
relations, psychological and logical, between the scientific study of
the ascertained facts of illusion and the philosophic determination of
what is illusory in knowledge as a whole, the two domains must be
clearly distinguished. On purely scientific ground we cannot answer the
question, "How far does illusion extend?" The solution of this question
must be handed over to the philosopher, as one aspect of his problem of
cognition.

One or two remarks may, perhaps, be hazarded in concluding this account
of the relation of the scientific to the philosophic problem of
illusion. Science, as we have seen, takes its stand on a stable
consensus, a body of commonly accepted belief. And this being so, it
would seem to follow, that so far as she is allowed to interest herself
in philosophic questions, she will naturally be disposed to ask, What
beliefs are shared in by all minds, so far as normal and developed? In
other words, she will be inclined to look at universality as the main
thing to be determined in the region of philosophic inquiry. The
metaphysical sceptic, fond of daring exploits, may break up as many
accepted ideas as he likes into illusory _debris_, provided only he has
some bit of reality left to take his stand on. Meanwhile, the scientific
mind, here agreeing with the practical mind, will ask, "Will the beliefs
thus said to be capable of being shown to be illusory ever cease to
exercise their hold on men's minds, including that of the iconoclast
himself? Is the mode of demonstration of such a kind as to be likely
ever to materially weaken the common-sense 'intuition'?"

This question would seem to be most directly answerable by a