confusing them; the power to confuse ideas that are not very
unlike, and that are presented to us in immediate sequence, is
mainly due to the fact of the impetus, so to speak, which the mind
has upon it. We always, I believe, make an effort to see every new
object as a repetition of the object last before us. Objects are
so varied, and present themselves so rapidly, that as a general
rule we renounce this effort too promptly to notice it, but it is
always there, and it is because of it that we are able to mistake,
and hence to evolve new mental and bodily developments. Where the
effort is successful, there is illusion; where nearly successful
but not quite, there is a shock and a sense of being puzzled--more
or less, as the case may be; where it is so obviously impossible as
not to be pursued, there is no perception of the effort at all.

Mr. Locke has been greatly praised for his essay upon human
understanding. An essay on human misunderstanding should be no
less interesting and important. Illusion to a small extent is one
of the main causes, if indeed it is not the main cause, of
progress, but it must be upon a small scale. All abortive
speculation, whether commercial or philosophical, is based upon it,
and much as we may abuse such speculation, we are, all of us, its
debtors.

Leonardo da Vinci says that Sandro Botticelli spoke slightingly of
landscape-painting, and called it "but a vain study, since by
throwing a sponge impregnated with various colours against a wall,
it leaves some spots upon it, which may appear like a landscape."
Leonardo da Vinci continues: "It is true that a variety of
compositions may be seen in such spots according to the disposition
of mind with which they are considered; such as heads of men,