engravings on the brain, as the followers of Des Cartes, and the
humoral pathologists in general; nor of an oscillating ether which was
to effect the same service for the nerves of the brain considered as
solid fibres, as the animal spirits perform for them under the notion
of hollow tubes, as Hartley teaches--nor finally, (with yet more
recent dreamers) of chemical compositions by elective affinity, or of
an electric light at once the immediate object and the ultimate organ
of inward vision, which rises to the brain like an Aurora Borealis,
and there, disporting in various shapes,--as the balance of plus and
minus, or negative and positive, is destroyed or re-established,--
images out both past and present. Aristotle delivers a just theory
without pretending to an hypothesis; or in other words a comprehensive
survey of the different facts, and of their relations to each other
without supposition, that is, a fact placed under a number of facts,
as their common support and explanation; though in the majority of
instances these hypotheses or suppositions better deserve the name of
upopoiaeseis, or suffictions. He uses indeed the word kinaeseis, to
express what we call representations or ideas, but he carefully
distinguishes them from material motion, designating the latter always
by annexing the words en topo, or kata topon. On the contrary, in his
treatise De Anima, he excludes place and motion from all the
operations of thought, whether representations or volitions, as
attributes utterly and absurdly heterogeneous.

The general law of association, or, more accurately, the common
condition under which all exciting causes act, and in which they may
be generalized, according to Aristotle is this. Ideas by having been
together acquire a power of recalling each other; or every partial
representation awakes the total representation of which it had been a
part. In the practical determination of this common principle to