We are gravely and repeatedly told that there is no effect without a cause, that the world did not make itself. But the universe is a cause, it is not an effect; it is not a work, it has not been made, because it is impossible that it should have been made. The world has always been; its existence is necessary, it is its own cause. Nature, whose essence is visibly to act and produce, requires not, to discharge her functions, an invisible mover, much more unknown than herself. Matter moves by its own energy, by a necessary consequence of its heterogeneity. The diversity of motion, or modes of mutual action, constitutes alone the diversity of matter. We distinguish beings from one another only by the different impressions or motions which they can communicate to our organs.
d’Holdbach in Good Sense