On whether there is a sense, with regard to providence, in which it may be said that merits are the cause of predestination:
The Apostle says (Titus 3:5): "Not by works of justice which we have done, but according to His mercy He saved us." But as He saved us, so He predestined that we should be saved. Therefore, foreknowledge of merits is not the cause or reason of predestination.Whether man can wish or do any good without grace:
Others said that pre-existing merits in this life are the reason and cause of the effect of predestination. For the Pelagians taught that the beginning of doing well came from us; and the consummaion from God: so that it came about that the effect of predestination was granted to one, and not to another, because the one made a beginning by preparing, whereas the other did not. But against this we have the saying of the Apostle (2 Corinthians 3:5), that "we are not sufficient to think anything of ourselves as of ourselves." Now no principle of action can be imagined previous to the act of thinking. Wherefore it cannot be said that anything begun in us can be the reason of the effect of predestination.
And so others said that merits following the effect of predestination are the reason of predestination; giving us to understand that God gives grace to a person, and pre-ordains that He will give it, because He knows beforehand that He will make good use of that grace, as if a king were to give a horse to a soldier because he knows he will make good use of it. But these seem to have drawn a distinction between that which flows from grace, and that which flows from free will, as if the same thing cannot come from both. It is, however, manifest that what is of grace is the effect of predestination; and this cannot be considered as the reason of predestination, since it is contained in the notion of predestination. Therefore, if anything else in us be the reason of predestination, it will outside the effect of predestination. Now there is no distinction between what flows from free will, and what is of predestination; as there is not distinction between what flows from a secondary cause and from a first cause. For the providence of God produces effects through the operation of secondary causes, as was above shown (22, 3). Wherefore, that which flows from free-will is also of predestination. We must say, therefore, that the effect of predestination may be considered in a twofold light--in one way, in particular; and thus there is no reason why one effect of predestination should not be the reason or cause of another; a subsequent effect being the reason of a previous effect, as its final cause; and the previous effect being the reason of the subsequent as its meritorious cause, which is reduced to the disposition of the matter. Thus we might say that God pre-ordained to give glory on account of merit, and that He pre-ordained to give grace to merit glory. In another way, the effect of predestination may be considered in general. Thus, it is impossible that the whole of the effect of predestination in general should have any cause as coming from us; because whatsoever is in man disposing him towards salvation, is all included under the effect of predestination; even the preparation for grace. For neither does this happen otherwise than by divine help, according to the prophet Jeremias (Lamentations 5:21): "convert us, O Lord, to Thee, and we shall be converted." Yet predestination has in this way, in regard to its effect, the goodness of God for its reason; towards which the whole effect of predestination is directed as to an end; and from which it proceeds, as from its first moving principle [ST I, Q23, A5; emphasis added].
The Apostle says (Romans 9:16): "It is not of him that willeth," namely, to will, "nor of him that runneth," namely to run, "but of God that showeth mercy." And Augustine says (De Corrept. et Gratia ii) that "without grace men do nothing good when they either think or wish or love or act."Whether man without grace and by his own natural powers can fulfil the commandments of the Law:
Man's nature may be looked at in two ways: first, in its integrity, as it was in our first parent before sin; secondly, as it is corrupted in us after the sin of our first parent. Now in both states human nature needs the help of God as First Mover, to do or wish any good whatsoever, as stated above (1). But in the state of integrity, as regards the sufficiency of the operative power, man by his natural endowments could wish and do the good proportionate to his nature, such as the good of acquired virtue; but not surpassing good, as the good of infused virtue. But in the state of corrupt nature, man falls short of what he could do by his nature, so that he is unable to fulfil it by his own natural powers. Yet because human nature is not altogether corrupted by sin, so as to be shorn of every natural good, even in the state of corrupted nature it can, by virtue of its natural endowments, work some particular good, as to build dwellings, plant vineyards, and the like; yet it cannot do all the good natural to it, so as to fall short in nothing; just as a sick man can of himself make some movements, yet he cannot be perfectly moved with the movements of one in health, unless by the help of medicine he be cured.
And thus in the state of perfect nature man needs a gratuitous strength superadded to natural strength for one reason, viz. in order to do and wish supernatural good; but for two reasons, in the state of corrupt nature, viz. in order to be healed, and furthermore in order to carry out works of supernatural virtue, which are meritorious. Beyond this, in both states man needs the Divine help, that he may be moved to act well [ST I-II, Q109, A2].
Augustine says (De Haeres. lxxxviii) that it is part of the Pelagian heresy that "they believe that without grace man can fulfil all the Divine commandments."Whether man can merit everlasting life without grace:
There are two ways of fulfilling the commandments of the Law. The first regards the substance of the works, as when a man does works of justice, fortitude, and of other virtues. And in this way man in the state of perfect nature could fulfil all the commandments of the Law; otherwise he would have been unable to sin in that state, since to sin is nothing else than to transgress the Divine commandments. But in the state of corrupted nature man cannot fulfil all the Divine commandments without healing grace. Secondly, the commandments of the law can be fulfilled, not merely as regards the substance of the act, but also as regards the mode of acting, i.e. their being done out of charity. And in this way, neither in the state of perfect nature, nor in the state of corrupt nature can man fulfil the commandments of the law without grace. Hence, Augustine (De Corrupt. et Grat. ii) having stated that "without grace men can do no good whatever," adds: "Not only do they know by its light what to do, but by its help they do lovingly what they know." Beyond this, in both states they need the help of God's motion in order to fulfil the commandments, as stated above (2,3) [ST I-II, Q109, A4; emphasis added].
Acts conducing to an end must be proportioned to the end. But no act exceeds the proportion of its active principle; and hence we see in natural things, that nothing can by its operation bring about an effect which exceeds its active force, but only such as is proportionate to its power. Now everlasting life is an end exceeding the proportion of human nature, as is clear from what we have said above (5, 5). Hence man, by his natural endowments, cannot produce meritorious works proportionate to everlasting life; and for this a higher force is needed, viz. the force of grace. And thus without grace man cannot merit everlasting life; yet he can perform works conducing to a good which is natural to man, as "to toil in the fields, to drink, to eat, or to have friends," and the like [ST I-II, Q109, A5; see also the same subject at I-II, Q114, A2].And so forth. But there is more, and rather than turn this blog post into a dissertation, I'll summarize.