n to our mind, necessarily
implies its existence out of that relation. But as so existing, it is
unknown: we believe _that_ it is; we know not _what_ it is. How far it
resembles, or how far it does not resemble, the object apprehended by us,
we cannot say, for we have no means of comparing the two together.

[AB] _Discussions_, p. 633.

Instead; therefore, of saying with Kant, that reason is subject to an
inevitable delusion, by which, it mistakes the regulative principles of
its own thoughts for the representations of real things, Hamilton would
say that the reason, while compelled to believe in the existence of these
real things, is not legitimately entitled to make any positive
representation of them as of such or such a nature; and that the
contradictions into which it falls when attempting to do so are due to an
illegitimate attempt to transcend the proper boundaries of positive
thought.

This theory does not, in itself, contain any statement of the mode in
which we perceive the material world, whether directly by presentation,
or indirectly by representative images; and perhaps it might, without any
great violence, be adapted to more than one of the current hypotheses on
this point. But that to which it most easily adjusts itself is that
maintained by Hamilton himself under the name of _Natural Realism_. To
speak of perception as a _relation_ between mind and matter, naturally
implies the presence of both correlatives; though each may be modified by
its contact with the other. The acid may act on the alkali, and the
alkali on the acid, in forming the neutral salt; but each of the
ingredients is as truly present as the other, though each enters into the
compound in a modified form. And this is equally the case in perception,
even if we suppose various media to intervene between the ultimate object
and the perceiving mind,--such, _e.g._, as the rays of light and the
sensitive organism in vision,--so long as these media are material, like
the ultimate object itself. Whether the object, properly so called, in
vision, be the rays of light in contact with the organ, or the body
emitting or reflecting those rays, is indifferent to the present
question, so long as a material object of some kind or other is supposed
to be perceived, and not merely an inmaterial representation of such an
object. To speak of our perceptions as mere modifications of mind
produced by an unknown cause, would be like maintaining that the aci