One might perhaps suggest that the only case in which it is correct to
say, without restriction, that I can do a certain
63.
thing, is that in which while
saying that I can do it, I actually do it, and that otherwise I ought to
say, “I can do it as far as … is
concerned”.
One may be inclined to think that only in the above case has a person
given a real proof of being able to do a thing.
65). But if we look at a
language-game in which the phrase “I can … ”
is used in this way (e.g., a game in which doing
a thing is taken as the only justification for saying that one is able
to do it), we see that there is not the
metaphysical
difference between this game and one in which other justifications
are accepted for saying “I can do
so-and-so”.
A game of the kind 65), by the way, shows us the real use of
the phrase, “If something happens it certainly can
happen”; an almost useless phrase in our language.
It sounds as though it had some very clear and deep meaning, but like
most of the general philosophical propositions it is meaningless
except in very special cases.
66). Make this clear to
yourself by imagining a language (similar to 49)) which has two
expressions for such sentences as, “I am lifting a fifty pound
weight”; one expression is used whenever the action is performed
as a test (say, before an athletic competition), the other
expression is used when the action is not performed as a test.