'It gives a very favourable idea of Sir W. Hamilton's
sincerity and devotion to truth (remarks Mr Mill, p. 247),
that he should have drawn from obscurity, and made generally
known, two cases so unfavourable to his own opinions.'

We think this remark perfectly just; and we would point out besides, in
appreciating Sir W. Hamilton's merits, that his appetite for facts was
useful to philosophy, as well as his appetite for speculation. But the
person whose usefulness to philosophy we prefer to bring into the
foreground, is Platner himself. He spent three weeks in patient
examination of this blind man, and the tenor of his report proves that
his sagacity in interpreting facts was equal to his patience in
collecting them. The rarity of all such careful and premeditated
observation of the facts of mind, appears to us one main reason why
(what Mr Mill calls) the _psychological_ theory finds so little
acceptance; and why those who maintain that what now seems a mental
integer was once a multiplicity of separate mental fragments, can
describe the antecedent steps of the change only as a _latens
processus_, which the reader never fully understands, and often will not
admit. Every man's mind is gradually built up from infancy to maturity;
the process is always going on before our eyes, yet the stages of
it--especially the earliest stages, the most pregnant with
instruction--are never studied and put on record by observers trained in
inductive logic, knowing beforehand what they ought to look for as the
_sine quâ non_ for proving or disproving any proposed theory. Such cases
as that cited by Platner--cases of one marked congenital defect of
sense, enabling us to apply the Method of Difference--are always within
reach; but few Platners are found to scrutinize and record them.
Historians of science describe to us the laborious and multiplied
observations, and the elaborate precaution for ensuring accuracy of