which without it would have been unexamined. Yet it is also itself very
liable to illusion. The evidence on which it rests is vague and
indefinite. The field of consciousness is never seen by us as a whole, but
only at particular points, which are always changing. The veil of language
intercepts facts. Hence it is desirable that in making an approach to the
study we should consider at the outset what are the kinds of error which
most easily affect it, and note the differences which separate it from
other branches of knowledge.

a. First, we observe the mind by the mind. It would seem therefore that
we are always in danger of leaving out the half of that which is the
subject of our enquiry. We come at once upon the difficulty of what is the
meaning of the word. Does it differ as subject and object in the same
manner? Can we suppose one set of feelings or one part of the mind to
interpret another? Is the introspecting thought the same with the thought
which is introspected? Has the mind the power of surveying its whole
domain at one and the same time?--No more than the eye can take in the
whole human body at a glance. Yet there may be a glimpse round the corner,
or a thought transferred in a moment from one point of view to another,
which enables us to see nearly the whole, if not at once, at any rate in
succession. Such glimpses will hardly enable us to contemplate from within
the mind in its true proportions. Hence the firmer ground of Psychology is
not the consciousness of inward feelings but the observation of external
actions, being the actions not only of ourselves, but of the innumerable
persons whom we come across in life.

b. The error of supposing partial or occasional explanation of mental
phenomena to be the only or complete ones. For example, we are disinclined
to admit of the spontaneity or discontinuity of the mind--it seems to us
like an effect without a cause, and therefore we suppose the train of our