Section — Slater, Manual of Moral Theology
5. Envy
Envy is sadness on account of another’s good, inasmuch as it is regarded as lessening one’s own. It is directly opposed to charity, which inclines us to rejoice in the good of our neighbour, and is mortally sinful if the matter is serious. We must carefully distinguish envy from various other dispositions which bear some resemblance to it. Thus, if one is sorry because another has obtained something desirable, thereby making it impossible for himself to obtain it, it is not envy but emulation, which in itself is praiseworthy. Sadness because another has obtained a post of influence of which he is unworthy, is not envy nor sinful. In the same way, if one is sad because his enemy has obtained the means of doing him harm, there is no sin in such a disposition. Envy comes in where an equal, or one who is not much more than an equal, rises in position, power, or influence, and his rise is regarded with ill will because it seems to lower one’s self.
p. i, 101–102
The ambitious are usually also envious, inasmuch as they see others enjoying what they wish to have for themselves. The mean-spirited, too, are commonly envious, since they look upon trivialities as matters of great importance, and the promotion of others, especially of the young, as a lowering of themselves.
p. i, 102