ODIUM. - It is generally the state of aversion, of persistent enmity toward any object whatsoever. It is to be considered either as a passion of the sensitive appetite or as a movement of the will.
As a passion it is aversion to evil, insofar as it is unbecoming and harmful to the subject (Sum. Theol., 1st-2nd, q. 29, a. 3). If properly regulated, it can be of the greatest help to the higher faculties by leading them to abhor with all their strength every true evil. Hatred as an act of the will is a state of aversion against a person or another object because they are bad or abominable ("odium abominatio") or because one desires evil for others so that it may harm them ("odium inimicitiae").
Hatred of abomination is opposed to the love of concupiscence, which wills the good for itself, insofar as one wills evil far from oneself. Hatred of enmity is opposed to the love of benevolence and of friendship (v. CHARITY), which leads one to desire the good for others, and it implies the will and the effort to procure evil in order to satisfy a desire for vengeance. Hatred of abomination is lawful (cf. Ps. 118, 113), if it does not exceed due measure, but it can easily lead to hatred of enmity, which is always unlawful, and it can reach the summit of malice and is usually called diabolical.
I. HATRED AGAINST GOD
Every hatred of God is a mortal sin in itself and by itself ("ex toto genere suo"); indeed, if it is hatred of enmity, it constitutes the gravest and most inexplicable of all sins. Theoretically it is inconceivable, and practically it is determined by a false conception of God himself. In very many cases, behind hatred toward God there is concealed instead an aversion toward opinions and persons that represent him.
II. ODIUM AGAINST ONESELF
It is that behavior directed against one's own self, which induces gloomy despair, self-hatred, cursing oneself, self-mutilation, suicide. Such conduct can be explained only by considering it as an abnormal psychological state, as the consequence of a morbid condition rather than as an action consciously directed against the very instinct of self-preservation and self-affirmation. But one also hates oneself when one does not reasonably provide for one's soul and body.
III. ODIUM AGAINST ONE'S NEIGHBOR
It takes concrete form in a psychological attitude of positive enmity toward another man, an enmity that generally originates from a more or less unjust behavior of the hated person and leads to denigrating him and, if possible, inflicting harm upon him; and it can occur both among individuals and among nations. A particular kind of o. toward one's neighbor is given by so-called "class o.," which is determined for the most part by circumstances of a personal and social character. Thus, for example, it is the one that arises in the poor against the rich, in the sick against the healthy, in apostates against the members of the community from which they have separated.
Against enemies, o. is reprehensible even from the merely natural point of view, inasmuch as it is directed at creatures of God and inasmuch as it is a cause of social ills; hence the condemnation of every o. or desire for vengeance, as intrinsically evil and gravely sinful ("ex genere suo").
O., finally, in all its directions and manifestations, is an impediment in direct opposition to that charity which Christ, confirming what had already been established in the natural order, preached and taught as the mark of his disciples, carrying it even to the forgiveness and love of enemies (v. CARITÀ).
Bibliography2 works
Francesco Ercolani