but this is a mistake; what is good is a will directed towards securing these false goods for other
people. This doctrine involves no logical contradiction, but it loses all plausibility if we
genuinely believe that what are commonly considered goods are worthless, for in that case the
virtuous will might just as well be directed to quite other ends.
There is, in fact, an element of sour grapes in Stoicism. We can't be happy, but we can be good;
let us therefore pretend that, so long as we are good, it doesn't matter being unhappy. This
doctrine is heroic, and, in a bad world, useful; but it is neither quite true nor, in a fundamental
sense, quite sincere.
Although the main importance of the Stoics was ethical, there were two respects in which their
teaching bore fruit in other fields. One of these is theory of knowledge; the other is the doctrine
of natural law and natural rights.
In theory of knowledge, in spite of Plato, they accepted perception; the deceptiveness of the
senses, they held, was really false judgement, and could be avoided by a little care. A Stoic
philosopher, Sphaerus, an immediate disciple of Zeno, was once invited to dinner by King
Ptolemy, who, having heard of this doctrine, offered him a pomegranate made of wax. The
philosopher proceeded to try to eat it, whereupon the king laughed at him. He replied that he
had felt no certainty of its being a real pomegranate, but had thought it unlikely that anything
inedible would be supplied at the royal table. * In this answer he appealed to a Stoic distinction,
between those things which can be known with certainty on the basis of perception, and those
which, on this basis, are only probable. On the whole, this doctrine was sane and scientific.
Another doctrine of theirs in theory of knowledge was more influential, though more
questionable. This was their belief in innate ideas and principles. Greek logic was wholly
deductive, and this raised the question of first premisses. First premisses had to be, at least in
part, general, and no method existed of proving them. The Stoics held that there are certain
principles which are luminously obvious, and are admitted by all men; these could be made, as
in Euclid Elements, the basis of deduction. Innate ideas, similarly, could be used as the starting-
point of definitions. This point of view was accepted throughout the Middle Ages, and even by
Descartes.
* Diogenes Laertius, Vol. VII, p. 177.