In another way we love God with our whole heart, mind, soul and strength, if nothing in us is lacking to divine love, if there is nothing which we do not, actually or habitually, refer to God. And a precept is given concerning this divine love.
[In the last chapter, St. Thomas described the perfection of love by which the whole power of a creature's faculties were turned to God. In this chapter he describes a lesser degree of perfection, according to which everything is at least habitually, or in one's ultimate orientation, ordered to God. It sounds a bit like the theory of the "fundamental option," which maintains that choices of concrete individual acts cannot separate a person from God, that this is only a matter of one's fundamental orientation. But what is St. Thomas saying here? When a person is ordered to an end, that end remains the goal of all the particular things he does on the way to the end, even when he is not actually thinking about the end. For example, when a person sits down to write a letter to a friend, then even when his thoughts are occupied with the attempt to recall events of previous days, or with the attempt to spell a difficult word correctly, he is doing these things for the sake of his friend. Similarly, if the primary reason a person has a job is to support his family, this motivation is the implicit motivation of the various tasks he does in his job, even though he doesn't explicitly think of his family every moment.]
First, man should refer all things to God as his end, as the Apostle says: "Whether you eat or drink, or whatsoever else you do, do all to the glory of God." (1 Cor 10:31). One fulfills this when one orders his life to God's service, and thus all the things that he does for himself, he virtually orders to God, unless they are things that lead away from God, such as sins: thus man loves God with his whole heart.
[Everyone naturally seeks a single ultimate goal in the sense of seeking to be happy, and indeed, seeking to live a life of happiness. We do many things that we could not give a precise reason for, but we perceive in a vague manner that they are elements of a happy life. Thus everything we do is, in a sense, for ourselves, insofar as each action is thought to be some component of or necessary for a happy life, and is implicitly or explicitly desired as such. Now, "when one orders his life to God's service," the goal of a "happy life" is seen and desired in light of a more perfect end, namely the fulfillment of God's will (It is important to note that these are not two separate ends–The fulfillment of God's will is not separated from or contrary to being happy, but includes and realizes this happiness). Thus, whatever a man does, he "does for himself" inasmuch as he does it as part of the happy life he desires. And therefore, such a man "virtually orders to God" everything he does–at least, as long as, in acting, he does not implicitly reject his previous life's goal of being happy by fulfilling God's will. The man who is writing a letter to his friend, if he begins deliberately drafting his letter in a manner liable to harm his friend but help himself, is not writing those sentences for the sake of his friend, even if he doesn't consciously reject the goal of writing for his friend, but is only thinking about the profit he can somehow derive from the friendship. Similarly, a man who concretely does something that is not suited for growing in charity, but hinders it, is not doing that concrete action for the sake of God, even if he doesn't reject it. And if he does something that is simply incompatible with charity, he not only is not doing that concrete action for the sake of God, but is no longer even acting as a whole for the sake of God.]
[Since the primary affection of the soul is love, it is by love for the end, by charity, that all things are referred to God as the end. St. Thomas thus goes on explain how the various elements of human life (intellect, will, actions) are referred to God by charity, and how these various aspects can be understood in the commandment to love God "with the whole heart, mind, soul, and strength."]
Secondly, man should subject his intellect to God, believing those things that are divinely revealed, according to the Apostle: "taking understanding captivity, unto the obedience of Christ" (2 Cor 10:5). Thus man loves God with his whole mind.
[Insofar as the intellect, with respect to matters that are not seen as manifestly true or false, is subject to the will's influence, it shares in the movement of the will. Thus a man may be said to love God with his mind, or intellect, inasmuch as his motivation to believe is his friendship with God, his love for him, and inasmuch as his belief is an expression of this friendship.]
Thirdly, all the things a man loves, he should love in God, and universally refer all his affection to the love of God; hence the Apostle says "whether we be transported in mind it is to God, or whether we be sober, it is for you; for the charity of Christ presses us" (2 Cor. v. 13). Thus man loves God with his whole soul.
Fourthly, man should derive all his external works, words and deeds from divine love, according to the Apostle: "Let all your things be done in love" (1 Cor 16:14), and thus a man loves God with all his strength.
[To "refer all his affection to the love of God" and to "derive all his external works" is not to be understood in an explicit and conscious sense, which pertained to the previous kind of perfection of love, but in a general sense–possibly explicit, but at any rate implicit–as explained in the first point about referring all things to God as an end.]
This is, then, the third mode of perfect divine love, to which all are bound by the necessity of precept. But the second mode is not possible to anyone in this life, unless he is at the same time a wayfarer and an enjoyer of beatitude, as was our Lord Jesus Christ.