Handbook of the History of Logic: - Fordham University Faculty

50 John Marenbon
mother of Christ, was purified of sin by his future death (the so-called ‘Immaculate
Conception’). The objection is then raised that, if so, then Christ must have died of
necessity. The problem, then, is a variant of the problem of prophecy and necessity,
which is itself one version of the problem of prescience. In the problem of prophecy,
A knows at t 1 that a proposition p about what happens at some future time t 2 is
true, and so it seems that what happens at t 2 cannot be contingent, because t 2
cannot turn out to be false if A knows it to be true. In the case of the Immaculate
Conception, the truth at t 1 of the proposition
17. Mary is purified of sin by Christ’s death at t 2
is incompatible with its turning out to be false that
18. Christ dies at t 2 .
Anselm tries to solve the difficulty by recourse to a line of thought similar
to that Peter Damian had used in his On Devine Omnipotence. He distinguishes
[Anselm, 1946, II, 125] genuine, preceding (praecedens) necessity from what he calls
‘sequent necessity’ (sequens necessitas). Genuine necessity involves constraint. It
is necessary that the sky revolves because ‘the violence of its natural condition
forces’ it. But in a case of sequent necessity, such as the necessity that you are
talking because (quia) you are talking, there is no compulsion. Although the
matter is not clear (especially since Anselm varies his connectives between ‘if’
(si), ‘because’ (quia) and ‘while’ (dum)), Anselm seems — just like Damian —
not to have the logical equipment to distinguish between
17. Necessarily (if x is what took place/is taking place/will take place, then x is
what took place/is taking place/will take place)
and
18. If x is what took place/is taking place/will take place, then x took place/is
taking place/will take place necessarily.
Since (17) is obviously true, he feels compelled to accept (18), which he does not
discriminate from it, but — like Damian again — describes the necessity involved
as being limited in a way that makes the force of (18) no more than that of
(17). Anselm then says that it is this sort of non-coercive, sequent necessity that
Aristotle talks about in On Interpretation and that it is by this necessity that it is
said that it was necessary for things to be as the ‘faith or prophecy’ about Christ’s
death said. Unfortunately, Anselm has not seen the seriousness of the problem
which faced Aristotle and which, in an even more serious form, faces him. He
is right to try to suggest, although he lacks the equipment to do so clearly, that
from the fact that, necessarily, if I am doing x, then I am doing x, itdoesnot
follow that I am necessarily doing x (except if ‘necessarily’ is drained of its ordinary
meaning). But he is unaware that the argument from prescience or prophecy gains
its force from the temporal element: when gaining knowledge of an event precedes