THUS have the opinions handed down by former writers upon Vital Principle been delineated; and now let us retrace our steps, and again, as if at the outset of our inquiry, endeavour to define what it is and what the most general expression for it.
We say, then, that essence is a particular genus of entities, and that of it part is matter, which in itself is not any one particular object, as it is other than form and species from which each object derives its particular denomination; and that, in the third place, there is the derivative from both these. Now matter is potentiality, species reality, and that in a twofold acceptation, as knowledge and as reflexion; but bodies, and above all natural bodies, seem to be essences; for they are, in fact, the origins of other bodies. Among natural bodies some have and some have not life; and by life we mean the faculties of self-nourishment, self-growth and self-decay. Thus,