ws of motion: nothing is so
appropriate, all the more since they are in accord with each other. But
there is to be found in them no absolute necessity, such as may compel us
to admit them, in the way one is compelled to admit the rules of logic, of
arithmetic and geometry.

347. It seems, when one considers the indifference of matter to motion and
to rest, that the largest body at rest could be carried along without any
resistance by the smallest body in motion, in which case there would be
action without reaction and an effect greater than its cause. There is also
no necessity to say of the motion of a ball which runs freely on an even,
horizontal plane, with a certain degree of speed, termed A, that this
motion must have the properties of that motion which it would have if it
were going with lesser speed in a boat, itself moving in the same direction
with the residue of the speed, to ensure that the ball, seen from the bank,
advance with the same degree A. For, although the same appearance of speed
and of direction results through this medium of the boat, it is not because
it is the same thing. Nevertheless it happens that the effects of the
collision of the balls in the boat, the motion in each one separately
combined with that of the boat giving the appearance of that which goes on
outside the boat, also give the appearance of the effects that these same
balls colliding would have outside the boat. All that is admirable, but one
does not see its absolute necessity. A movement on the two sides of the
right-angled triangle composes a movement on the hypotenuse; but it does
not follow that a ball moving on the hypotenuse must produce the effect of
two balls of its own size moving on the two sides: yet that is true.
Nothing is so appropriate as this result, and God has chosen the laws that
produce it: but one sees no geometrical necessity therein. Yet it is this
very lack of necessity which enhances the beauty of the laws that God has
chosen, wherein divers admirable axioms exist in conjunction, and it is
impossible for one to say which of them is the primary.

348. I have also shown that therein is observed that excellent law of
continuity, which I have perhaps been the first to state, and which is a
kind of touchstone whose test the rules of M. Descartes, of Father Fabry,
Father Pardies, Father de Malebranche and others cannot pass. In virtue of
this law, one must be able to regard rest as a movement vanishing [334