80. POWERS, FACULTIES AND FORCES.—A natural operative power, faculty, or force (δύναμις, _potentia_, _facultas_, _virtus agendi_) is a quality which renders the nature of the individual agent apt to elicit certain actions. By _impotence_ or _incapacity_ (ἀδυναμία, _impotentia_, _incapacitas_) Aristotle meant not an opposite kind of quality, in contradistinction to power or faculty, but only a _power of a weaker order_, differing _in degree_, not _in kind_, from the real power which renders an agent proximately capable of acting; such weaker capacities, for instance, as the infant’s power to walk, or the defective eyesight of the aged. It is to the individual subsisting person or thing that all the actions proceeding from the latter are ascribed: _actiones sunt suppositorum_: the “_suppositum_” or person is the _principium_ QUOD _agit_. And it acts in accordance with its nature; this latter is the _principium_ QUO _agens agit_: the nature is the substance or essence as a principle of the actions whereby the individual tends to realize its end. But is a created, finite nature the _immediate_ or _proximate_ principle of its activities, so that it is operative _per se_? Or is it only their _remote principle_, eliciting them not by itself but _only_ by means of _powers_, _faculties_, _forces_, which are themselves accidental perfections of the substance and _really distinct_ from it, qualities intermediate between the latter and its actions, being the _proximate_ principles of the latter? No doubt when any individual nature is acted upon by other agencies, when it undergoes real change under the influence of its environment, its _passive potentiality_ is being so far forth actualized. Moreover when the nature itself acts _immanently_, the term of such action remaining within the agent itself to actualize or perfect it, some _passive potentiality_ of the agent is being actualized. In these cases the nature before being thus actualized was really capable of such actualization. This _passive potentiality_, however, is itself nothing actual, it implies no actual perfection in the nature. But we must distinguish carefully from this _passive or receptive potentiality_ of a nature its _active or operative powers_—_potentiae operativae_. These may be themselves _actual perfections_ in the nature, _accidental_ perfections actually in the nature, and perhaps really distinct from it.