In the middle ages 201

ient, under penalty of not being at all. To deny

this sort of preexistence is equivalent to denying

change from one state to another, the evolution of

reality. What we call change would then be a series

of instantaneous appearances and disappearances

of substances, having no internal connections what-

ever, each with duration infinitesimally small. The

oak is potentially in the acorn ; if it were not there

potentially, how could it ever issue from it? On

the other hand, the oak is not potentially in a peb-

ble, rolled about by the sea, and which outwardly

might present a close resemblance to the acorn.

Act or actuaUty (the ^vTcXix^ta of Aristotle, the actus

of the scholastics) is any present sum-total of per-

fection. Potency (SuVa/xt? potentia of the scholas-

tics) is the aptitude to become that perfection. It

is imperfection and non-being, if you will ; but it is

not mere nothing, because non-being considered in

an already existing subject is endowed with the

germ of future actualization.

The coupling of act and potency therefore pene-

trates reality in its inmost depths. It explains all

the great conceptions of scholastic metaphysics.

Especially does it explain those two great doctrines,

in which we shall follow the play of act and po-

tency, — namely, the doctrine of substance and ac-

cident, and the doctrine of matter and form.

202 PHILOSOPHY AND CIVILIZATION

IV

The doctrine of substance and accident is thus

rounded out and clarified by the coupUng of act

and potency; indeed, an adequate understanding

of the former requires the latter. Thus, to say that

a being already constituted in its substantial de-

termination is changing, means that it is actually

realizing its potentialities, A child is already po-

tentially the powerful athlete he will some day be-

come. If he is destined to become a mathematician,

then already in the cradle he possesses this power,

or predisposition, whereas another infant is de-

prived of it. Quantitative and qualitative change,

change in the activities brought about by actual

being and in the activity undergone, — all of this

was able to he before being in fact.

Considered in the light of this theory, the doc-

trine of substance and accident loses its naive and

false significance. A growing oak, a living man,

a chemical individuality of any kind, each of the

myriad individual beings, is indeed an individual

substance becoming, because its quantity, qualities,

activities, relations are the becoming of its poten-

tialities. Leibnitz was really following this thomis-

tic doctrine when he said: "The present is preg-

nant with the future." But more than this. While

Leibnitz also taught the eternity and the immuta-

bility of substances, which he called monads,

Thomas and the scholastics go further into the