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] after having continually diminished, and likewise equality as an inequality that vanishes also, as would happen through the continual diminution of the greater of two unequal bodies, while the smaller retains its size. As a consequence of this consideration, the general rule for unequal bodies, or bodies in motion, must apply also to equal bodies or to bodies one of which is at rest, as to a particular case of the rule. This does result in the true laws of motion, and does not result in certain laws invented by M. Descartes and by some other men of talent, which already on that score alone prove to be ill-concerted, so that one may predict that experiment will not favour them. 349. These considerations make it plain that the laws of Nature regulating movements are neither entirely necessary nor entirely arbitrary. The middle course to be taken is that they are a choice of the most perfect wisdom. And this great example of the laws of motion shows with the utmost clarity how much difference there is between these three cases, to wit, firstly _an absolute necessity_, metaphysical or geometrical, which may be called blind, and which does not depend upon any but efficient causes; in the second place, _a moral necessity_, which comes from the free choice of wisdom in relation to final causes; and finally in the third place, _something absolutely arbitrary_, depending upon an indifference of equipoise, which is imagined, but which cannot exist, where there is no sufficient reason either in the efficient or in the final cause. Consequently one must conclude how mistaken it is to confuse either that which is absolutely necessary with that which is determined by the reason of the best, or the freedom that is determined by reason with a vague indifference.