which has no relation to sight, has been already sufficiently exposed
by the younger Reimarus, Maasz, and others, as outraging the very
axioms of mechanics in a scheme, the merit of which consists in its
being mechanical. Whether any other philosophy be possible, but the
mechanical; and again, whether the mechanical system can have any
claim to be called philosophy; are questions for another place. It is,
however, certain, that as long as we deny the former, and affirm the
latter, we must bewilder ourselves, whenever we would pierce into the
adyta of causation; and all that laborious conjecture can do, is to
fill up the gaps of fancy. Under that despotism of the eye (the
emancipation from which Pythagoras by his numeral, and Plato by his
musical, symbols, and both by geometric discipline, aimed at, as the
first propaideuma of the mind)--under this strong sensuous influence,
we are restless because invisible things are not the objects of
vision; and metaphysical systems, for the most part, become popular,
not for their truth, but in proportion as they attribute to causes a
susceptibility of being seen, if only our visual organs were
sufficiently powerful.

From a hundred possible confutations let one suffice. According to
this system the idea or vibration a from the external object A becomes
associable with the idea or vibration m from the external object M,
because the oscillation a propagated itself so as to re-produce the
oscillation m. But the original impression from M was essentially
different from the impression A: unless therefore different causes may
produce the same effect, the vibration a could never produce the
vibration m: and this therefore could never be the means, by which a
and m are associated. To understand this, the attentive reader need
only be reminded, that the ideas are themselves, in Hartley's system,
nothing more than their appropriate configurative vibrations. It is a