Their motion is uninterruptedly and reciprocally produced from each other; they are alternately causes and effects. Thus, they form a vast circle of generation and destruction--of combination and decomposition, which, it is quite reasonable to suppose, could never have had a beginning, and which, consequently can never have an end. In short, Nature is but an immense chain of causes and effects, which unceasingly flow from each other. The motion of particular beings depends on the general motion, which is itself maintained by individual motion. This is strengthened or weakened, accelerated or retarded, simplified or complicated, procreated or destroyed, by a variety of combinations and circumstances, which every moment change the directions, the tendency, the modes of existing, and of acting, of the different beings that receive its impulse. If it were true, as has been asserted by some philosophers, that every thing has a tendency to form one unique or single mass, and in that unique mass the instant should arrive when all was in _nisus_, all would eternally remain in this state; to all eternity there would be no more than one Being and one effort: this would be eternal and universal death. If we desire to go beyond this, to find the principle of action in matter, to trace the origin of things, it is for ever to fall back upon difficulties; it is absolutely to abridge the evidence of our senses; by which only we can understand, by which alone we can judge of the causes acting upon them, or the impulse by which they are set in action. Let us, therefore, content ourselves with saying WHAT is supported by our experience, and by all the evidence we are capable of understanding; against the truth of which not a shadow of proof, such as our reason can admit, has ever been adduced--which has been maintained by philosophers in every age--which theologians themselves have not denied, but which many of them have upheld; namely, that _matter always existed; that it moves by virtue of its essence; that all the phenomena of Nature is ascribable to the diversified motion of the variety of matter she contains; and which, like the phoenix, is continually regenerating out of its own ashes._ CHAP. III. _Of Matter.--Of its various Combinations.--Of its diversified Motion, or of the Course of Nature._