We are accustomed to speak of ideas as reproduced, as passed from mind to
mind, as similar or dissimilar to one another, and, in short, as if they
were substantial things; nor can any reasonable objection be raised to
such expressions. But taking the word “idea” in the sense of an event in
an individual consciousness, it is clear that an idea once past is gone
forever, and any supposed recurrence of it is another idea. These two
ideas are not present in the same state of consciousness, and therefore
cannot possibly be compared. To say, therefore, that they are similar
can only mean that an occult power from the depths of the soul forces
us to connect them in our thoughts after they are both no more. We may
note, here, in passing that of the two generally recognised principles of
association, contiguity and similarity, the former is a connection due to
a power without, the latter a connection due to a power within.
But what can it mean to say that ideas wholly past are thought of at
all, any longer? They are utterly unknowable. What distinct meaning can
attach to saying that an idea in the past in any way affects an idea in
the future, from which it is completely detached? A phrase between the
assertion and the denial of which there can in no case be any sensible
difference is mere gibberish.
I will not dwell further upon this point, because it is a commonplace of
philosophy.