First Physical Dissertation on the Bond Connecting Soul and Body

occurring among the Saline-Sulphureous particles of the aether, tempered and not excessive (so that it may be distinguished from the other species of fire, flame), from which it is that heat is said to be felt in the organ of touch. From this it is clear that the nature of this fire is nearly the same as what was asserted above regarding light. For fire, or heat, as far as it begins to exist, consists in a certain mode, namely, the motion of the Saline-Sulphureous aether particles as substances, which mode and motion ceasing, there is nothing in the individual, nor is it to be called heat unless those particles of aether are impelled into motion.

From this it becomes manifest that heat is not a particular substance. Whence it simultaneously follows that I can deservedly supersede all discussion concerning the bond between the World and Heat, which is sold as the spirit of the world. But if—though I would not wish to presume this—it is contended that those aether particles driven into motion are themselves fire, then the connection between this fire, as a body, and mundane bodies would be obvious. Yet there would occur a difficulty regarding the inquiry into the coupling between fire and souls, the other species of created things, since we know that the substances of souls are entirely superior to the sensible power of bodily touch. And this difficulty occurs everywhere, arising from the heterogeneity of substances in the World and the diverse relationship toward them, which ought to be inherent in one and the same nature of the World Soul.

In the last place, the opinion of the STOICS occurs, which COMENIUS and PHILO also maintain, and which