which sensation, by association with that of touch, becomes
extended, so to speak, over an external surface, and defined into
limited figures. We are not disposed to lay any greater stress than Dr
Brown himself upon the _image_ said to be traced upon the retina; but we
say that the eye, as well as the touch, immediately informs us of
external surface and definite figure.

There is, it is true, a _sensation_ of colour apart from the
_perception_. This may be separated, in our reflection, from all
external surface. It is a _pleasure_ which colour gives, and which
enters largely into the complex sentiments of beauty. But our notion of
colour itself we cannot dissociate from external surface: we cannot
think of colour but as something outward. And if it comes to us
originally under the condition of external surface, it must also present
itself originally under certain forms and figures; for only where the
whole field of vision is occupied by one unvaried colour, as when the
eye is fixed upon a cloudless sky, could there be the perception of
surface without some figure, more or less defined on it.

And why is it, that on a subject of this nature the manifest facts
witnessed in the whole animal creation are to be overlooked? If other
animals evidently, on the first opening of their eyes, see form, and
movement, and the whole world before them; does not this sufficiently
intimate the instantaneous knowledge which it is the nature of vision to
bestow? The human infant arrives, indeed, more slowly at the perfect use
of its senses. It arrives, also, more slowly at the perfect use of its
limbs. But we never conclude because it does not rise and skip about the
fields like a dropped lamb, that there is any essential difference
between its muscular powers and those of other animals of creation. Why
should we suppose that its vision is regulated by different laws merely
because it obtains the perfect use of its eyesight somewhat later?

Let us now turn from the imperfect analysis which the _sensational_
school presents, to the speculations of the _idealist_. It will be seen
that the hasty conclusions of the first gave a sort of basis for the
strange results to which the second would conduct us.

Kant looked in vain for the idea of extension, or of space, where the
philosophers had been seeking it, in the phenomena of sensation. He
pronounced, therefore, that it was not derivable from experience, did
not come to us from without, th