Objection 1: It would seem that Christ as man had not the use of free-will in the first instant of His conception. For a thing is, before it acts or operates. Now the use of free-will is an operation. Since, therefore, Christ's soul began to exist in the first instant of His conception, as was made clear above (Q. 33, A. 2), it seems impossible that He should have the use of free-will in the first instant of His conception.
Obj. 2: Further, the use of free-will consists in choice. But choice presupposes the deliberation of counsel: for the Philosopher says (Ethic. iii) that choice is "the desire of what has been previously the object of deliberation." Therefore it seems impossible that Christ should have had the use of free-will in the first instant of His conception.
Obj. 3: Further, the free-will is "a faculty of the will and reason," as stated in the First Part (Q. 83, A. 2, Obj. 2): consequently the use of free-will is an act of the will and the reason or intellect. But the act of the intellect presupposes an act of the senses; and this cannot exist without proper disposition of the organs--a condition which would seem impossible in the first instant of Christ's conception. Therefore it seems that Christ could not have the use of free-will at the first instant of His conception.
On the contrary, Augustine says in his book on the Trinity (Gregory: Regist. ix, Ep. 61): "As soon as the Word entered the womb, while retaining the reality of His Nature, He was made flesh, and a perfect man." But a perfect man has the use of free-will. Therefore Christ had the use of free-will in the first instant of His conception.
I answer that, As stated above (A. 1), spiritual perfection was becoming to the human nature which Christ took, which perfection He attained not by making progress, but by receiving it from the very first. Now ultimate perfection does not consist in power or habit, but in operation; wherefore it is said (De Anima ii, text. 5) that operation is a "second act." We must, therefore, say that in the first instant of His conception Christ had that operation of the soul which can be had in an instant. And such is the operation of the will and intellect, in which the use of free-will consists. For the operation of the intellect and will is sudden and instantaneous, much more, indeed, than corporeal vision; inasmuch as to understand, to will, and to feel, are not movements that may be described as "acts of an imperfect being," which attains perfection successively, but are "the acts of an already perfect being," as is said, De Anima iii, text. 28. We must therefore say that Christ had the use of free-will in the first instant of His conception.
Reply Obj. 1: Existence precedes action by nature, but not in time; but at the same time the agent has perfect existence, and begins to act unless it is hindered. Thus fire, as soon as it is generated, begins to give heat and light. The action of heating, however, is not terminated in an instant, but continues for a time; whereas the action of giving light is perfected in an instant. And such an operation is the use of free-will, as stated above.
Reply Obj. 2: As soon as counsel or deliberation is ended, there may be choice. But those who need the deliberation of counsel, as soon as this comes to an end are certain of what ought to be chosen: and consequently they choose at once. From this it is clear that the deliberation of counsel does not of necessity precede choice save for the purpose of inquiring into what is uncertain. But Christ, in the first instant of His conception, had the fulness of sanctifying grace, and in like manner the fulness of known truth; according to John 1:14: "Full of grace and truth." Wherefore, as being possessed of certainty about all things, He could choose at once in an instant.
Reply Obj. 3: Christ's intellect, in regard to His infused knowledge, could understand without turning to phantasms, as stated above (Q. 11, A. 2). Consequently His intellect and will could act without any action of the senses.
Nevertheless it was possible for Him, in the first instant of His conception, to have an operation of the senses: especially as to the sense of touch, which the infant can exercise in the womb even before it has received the rational soul, as is said, De Gener. Animal. ii, 3, 4. Wherefore, since Christ had the rational soul in the first instant of His conception, through His body being already fashioned and endowed with sensible organs, much more was it possible for Him to exercise the sense of touch in that same instant.