It is impossible to devise any satisfactory solution of this difficulty which will not at the same time upset the very foundation on which the Thomistic system rests, viz.: “_Nulla secunda causa potest operari, nisi sit efficaciter determinata a prima [scil. per applicationem potentiae ad actum]_,” that is to say, no secondary cause can act unless it be efficaciously determined by the First Cause by an application of the latter to the former as of potency to act. b) The Thomistic _gratia efficax_, conceived as a _praedeterminatio ad unum_, inevitably destroys free-will. α) It is important to state the question clearly: Not physical premotion as such,(727) but the implied connotation of _praevia determinatio ad unum_, is incompatible with the dogma of free-will. The freedom of the will does not consist in the pure contingency of an act, or in a merely passive indifference, but in active indifference either to will or not to will, to will thus or otherwise. Consequently every physical predetermination, in so far as it is a _determinatio ad unum_, must necessarily be destructive of free-will. Self-determination and physical predetermination by an extraneous will are mutually exclusive. Now the Thomists hold that the _gratia per se efficax_ operates in the manner of a supernatural _praedeterminatio ad unum_. If this were true, the will under the influence of efficacious grace would no longer be free. To perceive the full force of this argument it is necessary to keep in mind the Thomistic definition of _praemotio physica_ as “_actio Dei, quâ voluntatem humanam, priusquam se determinet, ita ad actum movet insuperabili virtute, ut voluntas nequeat omissionem sui actus cum illa praemotione coniungere_.”(728) That is to say: As the non-performance of an act by the will is owing simply and solely to the absence of the respective _praemotio physica_, so conversely, the performance of an act is conditioned simply and solely by the presence of a divine premotion; the will itself can neither obtain nor prevent such a premotion, because this would require a new premotion, which again depends entirely on the divine pleasure. If the will of man were thus inevitably predetermined by God, it could not in any sense of the term be called truly free. -------------------------------------