Is zeal or jealousy (zelus) an effect of love?
Zelus, however it is understood, is proportionate to the intensity of love. For to the extent that a power or force is more intense, to that extent it repels everything that is contrary to it or that stands in its way. So, too, love seeks to exclude everything that stands in its way. St. Thomas notes here that zelus differs according to whether we are speaking of love of concupiscence or love of friendship. With regard to love of concupiscence, love tends toward the exclusion of everything that threatens the acquisition or enjoyment of the object. “It is in this way that husbands are said to be jealous of their wives.” (St. Thomas doesn’t endorse this way of relating to one’s spouse; he simply points out that this is in fact the way husbands often relate to their wives. Of course, there are at least some cases when such an effect of love might be justified, even if there are many cases in which it is not.) In like manner, those who seek excellence are moved by “the zeal of envy” agains
