On Grace and Our Preparation for It

Summa Theologiae I-II, Q112, a2, and SCG III 160-162
 
Is preparation for grace required on man’s part? This is one of the rare articles in which Thomas answers both Yes and No. Grace can be understood in either of two ways: as the habitual gift of God (i.e., the infused virtues of faith, hope, and charity) or as supernatural help from God in general—i.e., any movement of the human soul toward the good. For grace in the first sense, some preparation is required, since the “forms” of the supernatural virtues can only come into “matter” that is suitably prepared for them. Thomas has in mind some act of consent on the part of the human being toward receiving grace, since God does not infuse the supernatural virtues into someone against his will.

In the second sense, no preparation is possible, since no movement of the soul toward God can occur without God’s help. Even the act of free-will by which we consent to the reception of the supernatural virtues is something worked in us by God.
 
Article 3. Is grace necessarily given to everyone who prepares for it?

Yes, but only because of God’s infallible concordance with His own decrees. Thomas considers an argument (in objection 3) based on Dionysius’s principle that good is naturally self-diffusive. Since grace is a higher good than any good of nature, it should be supremely self-diffusive, and so it should “automatically” flow into anyone whose heart is suitably prepared for it. In response, Thomas points out that the diffusion of good requires the action of an agent—a suitably prepared piece of matter is not automatically elevated to a higher state. And, since God is the agent and God acts freely in creating, the diffusion of grace depends on His free decrees. The self-diffusiveness of good does not require that God give every good to every possible creature.
 
Article 4: Is grace greater in one than in another?
 
Grace can be measured in two ways: in terms of the good to which it directs us, and in terms of the degree to which we receive the influence of the direction (subjectively). All grace is equal in the first sense, since it orders all to the supreme good of the beatific vision. In the second respect, grace can vary from person to person. The better one has prepared oneself for grace, the greater its influence in one’s life. But this too depends on the degree to which we are helped by God to prepare ourselves for grace. Hence, the fundamental source of inequality lies in God’s free choice.