Whatever efforts the philosopher makes to penetrate the secrets of nature, he never finds more, as we have many times repeated, than matter; various in itself, diversely modified in consequence of the motion it undergoes. Its whole, as well as its parts, displays only necessary causes producing necessary effects, which flow necessarily one out of the other: of which the mind, aided by experience, is more or less competent to discover the concatenation. In virtue of their specific properties, all the beings that come under our review, gravitate towards a centre--attract analogous matter--repel that which is unsuitable to combination--mutually receive and give impulse--acquire qualities--undergo modifications which maintain them in existence for a season--are born and dissolved by the operation of an inexorable decree, that obliges every thing, we behold to pass into a new mode of existence. It is to these continued vicissitudes that are to be ascribed all the phenomena, whether trivial or of magnitude; ordinary or extraordinary; known or unknown; simple or complicated; which are operated in the universe. It is by these mutations alone that we have any knowledge of nature: she is only mysterious to those who contemplate her through the veil of prejudice: her course is always simple to those who look at her without prepossession. To attribute the effects to which we are witnesses, to nature, to matter, variously combined with the motion that is inherent to it, is to give them an intelligible and known cause; to attempt to penetrate deeper, is to plunge ourselves into imaginary regions, where we find only a chaos of obscurities--where we are lost in an unfathomable abyss of incertitude. Let us then be content with contemplating nature, who, being self-existent, must in her essence possess motion; which cannot be conceived without properties, from which result perpetual action and re-action; or those continual efforts which give birth to such a numerous train of circumstances; in which a single molecule cannot be found, that does not necessarily occupy the place assigned to it, by immutable and necessary laws--that is for an instant in an absolute state of repose. What necessity can there exist to seek out of matter for a power to give it play, since its motion flows as necessarily out of its existence as its bulk, its form, its gravity, &c. since nature in inaction would no longer be nature?