inal law of mind, as universal as that which renders certain
sensations of sight and sound the immediate result of certain affections
of our eye or ear. To any being who is thus impressed with belief of
similarities of sequence, a different _consequent_ necessarily implies a
difference of the _antecedent_. In the case at present supposed,
however, the infant, who as yet knows nothing but himself, is conscious
of no previous difference; and the feeling of _resistance_ seems to him,
therefore, something _unknown_, which has its _cause in something that
is not himself_."--(Vol. i. p. 514.)

There is a certain pre-arrangement here of the circumstances to suit the
convenience of explanation. The little arm of the infant being very
closely fastened to its own little body, it could hardly move it fifty
or a thousand times in succession, or even once, without its muscular
sensation terminating in the sense of resistance, or pressure, which is
but another form of the sense of touch. In short, this would be always
sooner or later the consequent upon this muscular sensation. And it
appears very evident that "the little reasoner," more especially if he
held the same doctrine as Brown on the nature of cause and effect, would
look no further than the _first_ sensation for the cause of the
_second_. There would be few instances in his limited experience more
marked of invariable antecedence and consequence than this,--that the
muscular sensation would sooner or later be followed by a tactual one.
If we could suppose it possible, that the infant logician had to make
the discovery of an external world by an effort of reasoning upon its
sensations, we should say that this case was the least likely of any to
lead him to the discovery--the least likely to impel him to look out of
the circle of sensations for a cause of them.

Mere sensation of any kind, reason on it how we will, cannot account for
the perception of external objects, which is another and separate fact.
We are reduced to admit that it is by a simple primary law of our
constitution that the organs of sense (which may with equal propriety be
called the organs of perception) convey to us a knowledge of the
external world. We touch, and a tangible extended body is made known to
us; we open our eyes, and a visible body is before us.

Dr Brown, adopting and refining upon Berkeley's theory of vision,
attributes originally nothing more than the mere sensation of colour to
the eye,