Act, Actual, opposed to Potentiality, and Potential or Virtual in the old sense of the latter term.
Actus is the Latin word employed by the schoolmen as an equivalent to the ἐνέργεια of Aristotle, and potentialitas stands with them for his δύναμις.
As he spoke of things that are δὐναμει and things that are ἐνέργεια, so they of things in potentiâ and things in actu. The latter term has survived in the adjective actual and the adverb actually. In our older writers, however, the substantive act was used, not as with us, for an individual action, but in the technical sense of the Aristotelian philosophy. For example, take this sentence of Hooker: «God alone excepted, who actually and everlastingly is whatsoever He may be, and which cannot hereafter be that which now He is not; all other things are somewhat in possibility, which as yet they are not in act.«(1)
This distinction between existing δὐναμει and existing ἐνέργεια occupies an important place in Aristotelian philosophy. He illustrates it by referring to the presence δὐναμει of the statue in the marble, as opposed to the sculptured Mercury existing ἐνέργεια, to the half in the whole which can be separated from it, and then have an actual existence of its own, to wakefulness in him that is asleep which has a potential but not an actual reality, and the like.
Potentiality must not be identified with possibility. In possessing these distinct terms Latin terminology has an advantage over Greek, unless indeed we see the same distinction in the two words δυνατός and ἐνδεχομενός, when the latter is used in opposition to necessary. Though he is thrown on the word δύναμει and the adjective δυνατός, Aristotle is careful to note that nothing exists δύναμει of which the subject is not susceptible. Thus light has no potential existence in an inanimate thing, the finished statue none in water. Whereas anything is in one sense possible that does not involve contradiction.
Virtual and Virtuality were formerly synonymous with potential and potentiality. How these words came by their present, so different from their original, meaning, I know not. Johnson seemed aware of none but the present use, and failed to see that in the majority of his quotations the word is employed in its original one.
As there can be nothing potential in God, nothing that He might be, but is not, it has been well said that He is pure act.
The whole distinction between the potential and the actual is pregnant with consequence. It took a leading share in the theological controversies of the sixth century, and bears, as may be easily seen, on the whole question of original sin as distinguished from actual, the former being sin δύναμει, and the latter, as its name shows, sin ἐνέργεια. It also enters into the subject of Nominalism and Realism. Perhaps its aid might tend to an adjustment of that dispute. «The species is potentially in the genus, the genus is actually in the species.»(2) On the same principle we must say that the individual the res is potentially in the universal, the universal is actually in the individual. The genus energises in species, the species in the specimen, the universal in the individual. The difference between Aristotle’s and the modern employment of the word energy must be carefully kept in mind. Even in his own day, however, it would appear that he used it in a wider sense than the ordinary. Έπὶ πλέον γάρ ἐστω ή δύναμις καὶ ή ἐνέργεια τῶν μόνον λεγομένων κατὰ κίνησιν.(3) This remark would have been needless had the case been otherwise. In his use, however, οὺ μονον κινήσεώς ἐστιν ἐνέργεια ἀλλὰ καὶ ἀκινησίας.
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(1) Eccl. Pol. book I. v. 1.
(2) Lord Monboddo.
(3) Metaph. VIII. 1.
