nto non-natural regions may be wisely
encouraged when they satisfy an interest which is at bottom healthy and
may, at least indirectly, bring with it excellent fruits. As musicians
are an honour to society, so are dialecticians that have a single heart
and an exquisite patience. But somehow the benefit must redound to
society and to practical knowledge, or these abstracted hermits will
seem at first useless and at last mad. The logic of nonsense has a
subtle charm only because it can so easily be turned into the logic of
common sense. Empty dialectic is, as it were, the ballet of science: it
runs most neatly after nothing at all.

[Sidenote: No science _a priori_.]

Both physics and dialectic are contained in common knowledge, and when
carried further than men carry them daily life these sciences remain
essentially inevitable and essentially fallible. If science deserves
respect, it is not for being oracular but for being useful and
delightful, as seeing is. Understanding is nothing but seeing under and
seeing far. There is indeed a great mystery in knowledge, but this
mystery is present in the simplest memory or presumption. The sciences
have nothing to supply more fundamental than vulgar thinking or, as it
were, preliminary to it. They are simply elaborations of it; they accept
its pre-suppositions and carry on its ordinary processes. A pretence on
the philosopher's part that he could get behind or below human thinking,
that he could underpin, so to speak, his own childhood and the inherent
conventions of daily thought, would be pure imposture. A philosopher
can of course investigate the history of knowledge, he can analyse its
method and point out its assumptions; but he cannot know by other
authority than that which the vulgar know by, nor can his knowledge
begin with other unheard-of objects or deploy itself in advance over an
esoteric field. Every deeper investigation presupposes ordinary
perception and uses some at least of its data. Every possible discovery
_extends_ human knowledge. None can base human knowledge anew on a
deeper foundation or prefix an ante-experimental episode to experience.
We may construct a theory as disintegrating as we please about the
dialectical or empirical conditions of the experience given; we may
disclose its logical stratification or physical antecedents; but every
idea and principle used in such a theory must be borrowed from current
knowledge as it happens to lie in the philosop