were true, then every particular assertion of the form AP * AQ, would
not only be true, but would be an instance of a true formal implication
(namely "_x_P * _x_Q") and this, according to the proposed definition,
is all that "_x_P entails _x_Q" asserts. If, therefore, it were true,
it would again follow that all relational properties must be internal.
But that this view also is untrue appears to me perfectly obvious. The
proposition that I am in this room does "materially imply" that I am
more than five years old, since both are true; and the assertion that
it does is also an instance of a true formal implication, since it is
in fact true that all the persons in this room are more than five years
old; but nothing appears to me more obvious than that the second of
these two propositions can _not_ be deduced from the first--that the
kind of relation which holds between the premisses and conclusion of
a syllogism in _Barbara_ does _not_ hold between them. To put it in
another way: it seems to me quite obvious that the properties "being
a person in this room" and "being more than five years old" are not
related in the kind of way in which "being a right angle" _is_ related
to "being an angle," and which we express by saying that, in the case
of every term, the proposition that that term is an angle can be
deduced from the proposition that it is a right angle.
These are the only two suggestions as to the meaning of "_p_ entails
_q_" known to me, which, if true, would yield the result that (2)
does follow from (1), and that therefore all relational properties
are internal; and both of these, it seems to me, are obviously
false. All other suggested meanings, so far as I know, would leave
it true that (2) does not follow from (1), and therefore that I may
possibly be right in maintaining that some relational properties are
external. It might, for instance, be suggested that the last proposed
definition should be amended as follows--that we should say: "_p_
entails _q_" means "_p * q and_ this proposition is an instance of a
formal implication, which is not merely true but _self-evident,_ like
the laws of Formal Logic." This proposed definition would avoid the
paradoxes involved in Mr. Strachey's definition, since such true formal
implications as "all the persons in this room are more than five years
old" are certainly not self-evident; and, so far as I. can see, it may
state something which is in fact true of _p_ and _q,_ whenever and only
when _p_ entails _q._ I do not myself think that it gives the _meaning_
of "_p_ entails _q,_" since the kind of relation which I see to hold
between the premisses and conclusion of a syllogism seems to me to be
one which is purely "objective" in the sense that no psychological
term, such as is involved in the meaning of "self-evident," is involved
in its definition (if it has one). I am not, however, concerned to
dispute that some such definition of "_p_ entails _q_" as this may be
true.
Public-domain text, read in full here on John Shaqi.
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