(b) Habitually, one loves God with one’s whole heart when one is in the state of grace, preferring the love of God to every contrary love, although it is only at intervals that one is able to make acts of love. This is the essential mode of fulfilling the command of love here on earth. The whole heart must be given to God to the exclusion of love for any mortal sin, for mortal sin separates from God.
1558. The mode of loving God is expressed in various places in scripture (Deut., vi. 5; Matt., xxii. 37; Mark, xii. 30; Luke, x. 27), and there are slightly different interpretations given to the words by which it is conveyed. Thus, some exegetes see in the expressions “heart,” “soul,” “mind,” “strength,” synonymous significations of the one thought that God should be loved over all, and they think that different words are used only in order to give greater clearness and energy to the thought. But the following seems also a reliable explanation: (a) God must be loved with one’s whole heart, that is, the will must not intend any Last End other than God; (b) God must be loved with one’s whole mind, soul and strength, that is, the powers moved by the will—intellect, appetites and executive faculties—must be subject to God, must be regulated according to His will, and must carry out His commandments.
1559. Love of God with one’s whole heart excludes, then, opposite loves, but it does not exclude other loves that are not opposite or other dispositions that are less perfect. (a) Thus, love of God with one’s whole heart does not exclude love of self or of neighbor. (b) Love of God with one’s whole heart does not exclude the use of acts in reference to God that do not reach the height of disinterested love, such as acts of hope, gratitude, or fear (see 1033, 1054, 1093).
1560. There are various degrees of perfection in the fulfillment of the commandment of love of God.
(a) The most perfect fulfillment is found in heaven, where there is no turning from the love of God by grave sin, no impediment to its exercise by venial sin, and no interruption of its act by other occupations.
(b) The more perfect fulfillment of this commandment found on earth is modelled on the love of God exercised by the Saints in heaven, and the nearer one approaches to the model, the better does one fulfill the commandment. Thus, he who avoids not only what is against charity (i.e., mortal sin), but also, as far as possible, what is aside from charity (i.e., venial sin), loves God more perfectly than one who is careless about venial sin; and he who shuns, not only things unlawful that are harmful to charity, but also things lawful that interrupt the exercise of charity, loves God more, other things being equal, than another who avoids the unlawful, but whose mind is greatly occupied with lawful temporal matters.
(c) The ordinarily perfect fulfillment of the commandment is found in all those who, both in their internal and in their external acts, avoid all that is contrary to the love of God, although they fall into venial sin and are mostly occupied with temporal affairs. Thus is charity the bond of perfection (Col, iii. 14), the tie that binds man to his highest good; those who keep the commandments for its sake are followers after perfection, those who embrace counsels for its sake are in the state of perfection.
1561. The Commandment of Love of Self.—Love of self is understood in many senses. (a) According to its moral character, love of self is either sinful or virtuous, and virtuous self-love is either natural or supernatural (as was explained in 1136). (b) According to its physical character, love of self is either innate or elicited. Innate love of self is the tendency of nature to desire what pertains to the perfection of self, such as existence and its preservation (see 1108). Elicited love of self is the choice on the part of the reason and will of an ultimate happiness for self and of the means thereto.
1562. Charity obliges each one capable of precept to an elicited supernatural love of self. The obligation is grave for the following reasons: (a) the love of God includes love of self, for we cannot love God truly unless we also love those things that are His, especially His rational creatures made to His image and destined for His society; (b) the love of neighbor supposes love of self, for the commandment of love (Matt., xxii. 39) offers love of self as the model for love of others.
1563. The goods which the law of charity to self requires one to desire and seek after, are all those things that are necessary for the attainment of one’s happiness and due perfection.