71. SUBSTANCE AND NATURE.—We have already pointed out (13) that the terms “essence,” “substance,” and “nature” denote what is really the same thing, regarded under different aspects. The term “essence” is somewhat wider than “substance,” inasmuch as it means “what a thing is,” whether the thing be a substance, an accident, or a concrete existing individual including substance and accidents. The traditional meaning of the term “nature” in Aristotelian and scholastic philosophy is unmistakable. It means the essence or substance of an individual person or thing, regarded as _the fundamental principle of the latter’s activities_. Every finite individual comes into existence incomplete, having no doubt its _essential_ perfections and properties _actually_, but its _intermediate_ and _final_ perfections only _potentially_ (47). These it realizes gradually, through the exercise of its connatural activities. Every being is essentially intended for activity of some sort: “Omne ens est propter suam operationem,” says St. Thomas. And by the constant interplay of their activities these beings realize and sustain the universal order which makes the world a _cosmos_. There is in all things an immanent purpose or finality which enables us to speak of the whole system which they form as “Universal _Nature_”.(281) Therefore what we call a _substance_ or _essence_ from the _static_ point of view we call a _nature_ when we consider it from the _dynamic_ standpoint, or as an agent.(282) No doubt the forces, faculties and powers, the active and passive accidental principles, whereby such an agent exerts and undergoes action, are the _proximate_ principles of all this action and change, but the _remote_ and fundamental principle of the latter is the essence or substance of the agent itself, in other words its _nature_.