ist of which Hume takes no
cognizance.

Kant answered the latter question in the affirmative, in the _Kritik der
reinen Vernunft_, and thereby made one of the greatest advances ever
effected in philosophy; though it must be confessed that the German
philosopher's exposition of his views is so perplexed in style, so
burdened with the weight of a cumbrous and uncouth scholasticism, that
it is easy to confound the unessential parts of his system with those
which are of profound importance. His baggage train is bigger than his
army, and the student who attacks him is too often led to suspect he has
won a position when he has only captured a mob of useless
camp-followers.

In his _Principles of Psychology_, Mr. Herbert Spencer appears to me to
have brought out the essential truth which underlies Kant's doctrine in
a far clearer manner than any one else; but, for the purpose of the
present summary view of Hume's philosophy, it must suffice if I state
the matter in my own way, giving the broad outlines, without entering
into the details of a large and difficult discussion.

When a red light flashes across the field of vision, there arises in the
mind an "impression of sensation"--which we call red. It appears to me
that this sensation, red, is a something which may exist altogether
independently of any other impression, or idea, as an individual
existence. It is perfectly conceivable that a sentient being should have
no sense but vision, and that he should have spent his existence in
absolute darkness, with the exception of one solitary flash of red
light. That momentary illumination would suffice to give him the
impression under consideration; and the whole content of his
consciousness might be that impression; and, if he were endowed with
memory, its idea.

Such being the state of affairs, suppose a second flash of red light to
follow the first. If there were no memory of the latter, the state of
the mind on the second occasion would simply be a repetition of that
which occurred before. There would be merely another impression.

But suppose memory to exist, and that an idea of the first impression is
generated; then, if the supposed sentient being were like ourselves,
there might arise in his mind two altogether new impressions. The one is
the feeling of the _succession_ of the two impressions, the other is the
feeling of their _similarity_.

Yet a third case is conceivable. Suppose two flashes of red light to
occur