Nisus  

"Some of the ancient Greek philosophers taught a version of hylozoism, as they, however vaguely, conceived the elemental matter as being in some sense animate if not actually conscious and conative (a directed effort, a striving or tendency; a nisus). The nisus concept was resurrected by d'Holbach in The System of Nature: "Natural philosophers, for the most part, seem not to have sufficiently reflected on what they call the nisus ; that is to say, the incessant efforts one body is making on another, but which, notwithstanding, appear, to our superficial observation, to enjoy the most perfect repose. A stone of five hundred weight seems at rest on the earth, nevertheless, it never ceases for an instant to press with force upon- the earth, which resists or repulses it in its turn."" --Sholem Stein