s his own self-destruction.'
This objection has been sufficiently overthrown: it is only a moral
necessity; and it is always a happy necessity to be bound to act in
accordance with the rules of perfect wisdom.

345. Moreover, it appears to me that the reason for the belief held by many
that the laws of motion are arbitrary comes from the fact that few people
have properly examined them. It is known now that M. Descartes was much
mistaken in his statement of them. I have proved conclusively that
conservation of the same quantity of motion cannot occur, but I consider
that the same quantity of force is conserved, whether absolute or directive
and respective, whether total or partial. My principles, which carry this
subject as far as it can go, have not yet been published in full; but I
have communicated them to friends competent to judge of them, who have
approved them, and have converted some other persons of acknowledged
erudition and ability. I discovered at the same time that the laws of
motion actually existing in Nature, and confirmed by experiments, are not
in reality absolutely demonstrable, as a geometrical proposition would be;
but neither is it necessary that they be so. They do not spring entirely
from the principle of necessity, but rather from the principle of
perfection and order; they are an effect of the choice and the wisdom of
God. I can demonstrate these laws in divers ways, but must always assume
something that is not of an absolutely geometrical necessity. Thus these
admirable laws are wonderful evidence of an intelligent and free being, as
opposed to the system of absolute and brute necessity, advocated by Strato
or Spinoza.

346. I have found that one may account for these laws by assuming that the
effect is always equal in force to its cause, or, which amounts to the same
thing, that the same force is conserved always: but this axiom of higher
philosophy cannot be demonstrated geometrically. One may again apply other
principles of like nature, for instance the principle that action is always
equal to reaction, one which assumes in things a distaste for external
change, and cannot be derived either from extension or impenetrability; and
that other principle, that a simple movement has the same properties as
those which might belong to a compound movement such as would produce [333]
the same phenomena of locomotion. These assumptions are very plausible, and
are successful as an explanation of the la