LXXX. I am so far from believing, that the subtil matter is the _primum mobile_, or first mover of every thing, that I am inclined to think, it moves nothing. My reason for this opinion, is as follows. The more fluid a matter is, so much the less impulse it makes on any body it encounters. Thus we see, that water gives a much less violent shock to a wall, than any other solid body of equal size, that may be forcibly driven against it; and air, a much less than water. No building could stand against, or resist a moderate gale of wind, if the air was as solid as water. The subtil matter then, according to the doctrine of the Cartesians, being infinitely fluid, can have but little impulse, or be able to impress but little agitation or motion, on the bodies it encounters. This consequence to me, is clear and plain; because, if in proportion to the augmentation of its fluidity, the impulse of a body is lessened, when the fluidity comes to be infinite, the impulse will cease totally. From hence it would follow, that there is no body whatever, which could be moved by the impulse of the subtil matter. LXXXI. But admitting that it has power, as the Cartesians pretend, to move the insensible particles of the mixtures; it will not follow from thence, that it furnishes us with an explanation of the present phenomenon. For in the first place, the subtil matter, if it has any impulse, exercises it on the particles of the juice the instant that it is pressed from the grape; and even perhaps did it before, while the liquor was contained within the outside skin or covering. How then does it happen, that it did not sooner excite that tumult, which is the symptom and property of fermentation? Secondly, how can the acids and alkalies be said to produce this effect? for, according to the doctrine of the Cartesians, of whatever particles the mixtures consist, the subtil matter would set them in motion, for that there is no mixture whatever, impenetrable to its extreme subtilty. Thirdly, how can those exceeding slow fermentations, which are years before they manifest themselves, as in the instance of treacle, be attributed to the rapid and swift motion of the subtil matter? SECT. XXI.