And because the like happens in all the other passions, to wit, that they are principally caused by the spirits contained in the cavities of the brain--seeing they direct their course towards the nerves which serve to enlarge or straighten the orifices of the heart either to thrust the blood in the other parts differently to it, or whatsoever other way it be, to feed the self same passion--it may be clearly understood by this: wherefore, I formerly inserted in my definition that they are caused by some peculiar motion of the spirits.