In the middle ages 267

state, — the fact of creation. The same also holds

true concerning the principles of the natural sci-

ences. Hence, such principles are not knowable by

mere analysis and comparison of their subject and

their predicate (per se notae) ; they manifestly rest

on observation and on experience {per aliud nota) ^

II

On the other hand, the world of limited existence

involves change, and scholasticism studied with

care the problem of change. The doctrine of act

and potency, — the actuality and potentiality in

each changing being — is nothing but their solution

of this problem.^ Change appears everywhere in

the physical world. But change itself follows cer-

tain uniformities; it is dominated by finalit3^ The

unvarying return of the seasons, the movements of

the planets, the cycle of physical and chemical laws,

the recurrence of vital phenomena in plants and

animals, — all of these exhibit the striking regular-

ity which is inherent in the realm of change. In so

far as one considers inorganic beings, the vegetable

and animal world, this same recurrence admits of

no exception. It is not only the species which are

fixed; the activities exhibited by the most diverse

- On the scholastic distinction between judgments per se nota and

per aliud nota (aliud here means observation and experience), see

Mercier, Logique, Louvain, 1919, pp. 135 ff. Cf. Thomas Aquinas, De

anima, II, 14,

3 See above ch. IX, iii.

268 PHILOSOPHY AND CIVILIZATION

individuals beings do not vary. In regard to evolu-

tion, as we understand it today, the dynamic meta-

physics of scholasticism neither includes nor ex-

cludes the change of one species into another. The

problem did not present itself in the thirteenth

century. Neither the theory of transformism nor

the theory of mutation is irreconcilable with the

scholastic theory of the world. Indeed, as we have

seen above, a substance transforms itself always

into another species of substance, — it does not mat-

ter how.

But human acts, are they bomid by the same uni-

formities, — or, on the contrary, is human progress

really possible? The question is the more interest-

ing because the thirteenth century believed that it

had realized a state of stable equilibrium, and be-

cause their extraordinary optimism lead them to

believe that they had arrived at a state close to

perfection. Accordingly it is necessary to explain

how they conceived of hmnanity as having tra-

versed the lower stages in order to arrive at this

degree of perfection.

A precise formulation is furnished by their meta-

physical psychology. Human nature is the same in

all men, and whatever rests on this nature is stable

and uniform. But the faculties, — the direct source

of activities — differ from man to man, in power and

in flexibility. The intelligence and the will are

energetic in a greater or a less degree ; they are sus-

ceptible of being perfected by education, and this