If I must accept general laws whose essential relation to matter is unperceived by me, how much further have I got?  These laws, not being real things, not being substances, have therefore some other basis unknown to me.  Experiment and observation have acquainted us with the laws of motion; these laws determine the results without showing their causes; they are quite inadequate to explain the system of the world and the course of the universe.  With the help of dice Descartes made heaven and earth; but he could not set his dice in motion, nor start the action of his centrifugal force without the help of rotation.  Newton discovered the law of gravitation; but gravitation alone would soon reduce the universe to a motionless mass; he was compelled to add a projectile force to account for the elliptical course of the celestial bodies; let Newton show us the hand that launched the planets in the tangent of their orbits.

The first causes of motion are not to be found in matter; matter receives and transmits motion, but does not produce it.  The more I observe the action and reaction of the forces of nature playing on one another, the more I see that we must always go back from one effect to another, till we arrive at a first cause in some will; for to assume an infinite succession of causes is to assume that there is no first cause.  In a word, no motion which is not caused by another motion can take place, except by a spontaneous, voluntary action; inanimate bodies have no action but motion, and there is no real action without will.  This is my first principle.  I believe, therefore, that there is a will which sets the universe in motion and gives life to nature.  This is my first dogma, or the first article of my creed.

How does a will produce a physical and corporeal action?  I cannot tell, but I perceive that it does so in myself; I will to do something and I do it; I will to move my body and it moves, but if an inanimate body, when at rest, should begin to move itself, the thing is incomprehensible and without precedent.  The will is known to me in its action, not in its nature.  I know this will as a cause of motion, but to conceive of matter as producing motion is clearly to conceive of an effect without a cause, which is not to conceive at all.

It is no more possible for me to conceive how my will moves my body than to conceive how my sensations affect my mind.  I do not even know why one of these mysteries has seemed less inexplicable than the other.  For my own part, whether I am active or passive, the means of union of the two substances seem to me absolutely incomprehensible.  It is very strange that people make this very incomprehensibility a step towards the compounding of the two substances, as if operations so different in kind were more easily explained in one case than in two.