Chapter 117 — That we are directed by the divine law to the love of our neighbor

From this it follows that the divine law aims at the love of our neighbor.

For there should be union of affection between those who have one common end. Now, men have one common last end, namely happiness, to which they are directed by God. Therefore, men should be united together by mutual love.

Again. Whosoever loves a man loves those whom he loves, and those who are his kindred. Now, men are loved by God, since he prepared for them a last end consisting in the enjoyment of himself. Therefore, as a man is a lover of God, so must he be a lover of his neighbor.

Moreover. Since man by nature is a social animal, (Nicomachean Ethics 1.7.) he needs assistance from other men in order to obtain his own end. Now this is most suitably done if men love one another mutually. Hence the law of God, which directs men to their last end, commands us to love one another.

Again. In order to apply himself to divine things, man needs calm and peace. Now mutual love, more than anything else, removes the obstacles to peace. Seeing, then, that the divine law directs men to apply themselves to divine things, we must conclude that this same law leads men to love one another.

Further. The divine law is offered to man in aid of the natural law. Now it is natural to all men to love one another: a proof of this is that a man, by a kind of natural instinct, comes to the assistance of anyone even unknown that is in need—for instance, by warning him if he should have taken the wrong road, by helping him to rise if he should have fallen, and so forth—as though every man were intimate and friendly with his fellow-man. (Nicomachean Ethics 8.1.) Therefore, mutual love is prescribed to man by the divine law.

Therefore, it is said: This is my commandment, that you love one another (John 15:12); and: This commandment we have from him, that he who loves God should love his brother also (1 John 4:21); and that the second commandment is: You shall love your neighbor (Matt 22:39).