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 qua 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
observation, which recent chemical and physical inquirers have found
indispensable for the establishment of their results. We cannot,
therefore, be surprised that mental philosophers, dealing with facts
even more obscure, and careless about enlarging, varying,
authenticating their records of particular facts, should have had
little success in establishing any results at all.

But if even those, who adopt the psychological theory, have been remiss
in the observation of particular mental facts,--those who deny the
theory have been far more than remiss; they have been blind to obvious
facts contradicting the principles which they lay down. Mr Mill, in
chap, xiv., deals with this denial, common to Mr Mansel with Sir W.
Hamilton. That philosophers so eminent as both of them should declare
confidently--'what I cannot but think must be _a priori_, or original to
thought; it cannot be engendered by experience upon custom' (p.
264)--appears to us as extraordinary as it does to Mr Mill. Though no
one ever surpassed Sir W. Hamilton in large acquaintance with the actual
diversities of human belief, and human incapacities of believing--yet he
never seems to have