is here used in the special and restricted sense of Plato. Not
everything that we should call knowledge is recollection.
The sensuous element in my perception that this paper is
white is not recollection, since, as being merely sensuous,
it is not, in Plato’s opinion, to be called knowledge. Here,
as elsewhere, he confines the term {213} to rational knowl-
edge, that is to say, knowledge of the Ideas, though it is
doubtful whether he is wholly consistent with himself in
the matter, especially in regard to mathematical knowl-
edge. It must also be noted that this doctrine has nothing
in common with the Oriental doctrine of the memory of
our past lives upon the earth. An example of this is found
in the Buddhist Jàtakas, where the Buddha relates from
memory many things that happened to him in the body in
his previous births. Plato’s doctrine is quite different. It
refers only to recollection of the experiences of the soul in
its disembodied state in the world of Ideas.
The reasons assigned by Plato for believing in this doctrine
may be reduced to two. Firstly, knowledge of the Ideas can-
not be derived from the senses, because the Idea is never
pure in its sensuous manifestation, but always mixed. The
one beauty, for example, is only found in experience mixed
with the ugly. The second reason is more striking. And,
if the doctrine of recollection is itself fantastic, this, the
chief reason upon which Plato bases it, is interesting and
important. He pointed out that mathematical knowledge
seems to be innate in the mind. It is neither imparted to
us by instruction, nor is it gained from experience. Plato,
in fact, came within an ace of discovering what, in modern
times, is called the distinction between necessary and con-
tingent knowledge, a distinction which was made by Kant
the basis of most far-reaching developments in philosophy.
The character of necessity attaches to rational knowledge,
but not to sensuous. To explain this distinction, we may
take as our example of rational knowledge such a proposi-
tion as that two {214} and two make four. This does not
mean merely that, as a matter of fact, every two objects
and every other two objects, with which we have tried the
experiment, make four. It is not merely a fact, it is a ne-
cessity. It is not merely that two and two do make four,
but that they must make four. It is inconceivable that they
should not. We have not got to go and see whether, in each
new case, they do so. We know beforehand that they will,
because they must. It is quite otherwise with such a propo-
sition as, “gold is yellow.” There is no necessity about it. It
is merely a fact. For all anybody can see to the contrary it
might just as well be blue. There is nothing inconceivable
about its being blue, as there is about two and two making
five. Of course, that gold is yellow is no doubt a mechanical
necessity, that is, it is determined by causes, and in that
sense could not be otherwise. But it is not a logical neces-
sity. It is not a logical contradiction to imagine blue gold,
as it would be to imagine two and two making five. Any
other proposition in mathematics possesses the same ne-
cessity. That the angles at the base of an isosceles triangle
are equal is a necessary proposition. It could not be oth-
erwise without contradiction. Its opposite is unthinkable.
But that Socrates is standing is not a necessary truth. He
might just as well be sitting.Since a mathematical proposition is necessarily true, its