Thomas started from that point, already far from theoretic freedom.  “We are masters of our acts,” he began, “in the sense that we can choose such and such a thing; now, we have not to choose our end, but the means that relate to it, as Aristotle says.”  Unfortunately, even this trenchant amputation of man’s free energies would not accord with fact or with logic.  Experience proved that man’s power of choice in action was very far from absolute, and logic seemed to require that every choice should have some predetermining cause which decided the will to act.  Science affirmed that choice was not free,—­could not be free,—­without abandoning the unity of force and the foundation of law.  Society insisted that its choice must be left free, whatever became of science or unity.  Saint Thomas was required to illustrate the theory of “liberum arbitrium” by choosing a path through these difficulties, where path there was obviously none.

Thomas’s method of treating this problem was sure to be as scientific as the vaulting of a Gothic arch.  Indeed, one follows it most easily by translating his school-vocabulary into modern technical terms.  With very slight straining of equivalents, Thomas might now be written thus:—­

By the term God, is meant a prime motor which supplies all energy to the universe, and acts directly on man as well as on all other creatures, moving him as a mechanical motor might do; but man, being specially provided with an organism more complex than the organisms of other creatures, enjoys an exceptional capacity for reflex action,—­a power of reflection,—­which enables him within certain limits to choose between paths; and this singular capacity is called free choice or free will.  Of course, the reflection is not choice, and though a man’s mind reflected as perfectly as the facets of a lighthouse lantern, it would never reach a choice without an energy which impels it to act.

Now let us read Saint Thomas:—­

Some kind of an agent is required to determine one’s choice; that agent is reflection.  Man reflects, then, in order to learn what choice to make between the two acts which offer themselves.  But reflection is, in its turn, a faculty of doing opposite things, for we can reflect or not reflect; and we are no further forward than before.  One cannot carry back this process infinitely, for in that case one would never decide.  The fixed point is not in man, since we meet in him, as a being apart by himself, only the alternative faculties; we must, therefore, recur to the intervention of an exterior agent who shall impress on our will a movement capable of putting an end to its hesitations:—­That exterior agent is nothing else than God!