The thing indeed would imply no
contradiction in itself if the effect did not follow; and therein lies
contingency. The better to understand this point, we must take into account
that there are two great principles of our arguments. The one is the
principle of _contradiction_, stating that of two contradictory
propositions the one is true, the other false; the other principle is that
of the _determinant reason_: it states that nothing ever comes to pass
without there being a cause or at least a reason determining it, that is,
something to give an _a priori_ reason why it is existent rather than
non-existent, and in this wise rather than in any other. This great
principle holds for all events, and a contrary instance will never be
supplied: and although more often than not we are insufficiently [148]
acquainted with these determinant reasons, we perceive nevertheless that
there are such. Were it not for this great principle we could never prove
the existence of God, and we should lose an infinitude of very just and
very profitable arguments whereof it is the foundation; moreover, it
suffers no exception, for otherwise its force would be weakened. Besides,
nothing is so weak as those systems where all is unsteady and full of
exceptions. That fault cannot be laid to the charge of the system I
approve, where everything happens in accordance with general rules that at
most are mutually restrictive.

45. We must therefore not imagine with some Schoolmen, whose ideas tend
towards the chimerical, that free contingent futurities have the privilege
of exemption from this general rule of the nature of things. There is
always a prevailing reason which prompts the will to its choice, and for
the maintenance of freedom for the will it suffices that this reason should
incline without necessitating. That is also the opinion of all the
ancients, of Plato, of Aristotle, of St. Augustine. The will is never
prompted to action save by the representation of the good, which prevails
over the opposite representations. This is admitted even in relation to
God, the good angels and the souls in bliss: and it is acknowledged that
they are none the less free in consequence of that. God fails not to choose
the best, but he is not constrained so to do: nay, more, there is no
necessity in the object of God's choice, for another sequence of things is
equally possible. For that very reason the choice is free and independent
of necessity, because it