The Catechism lists the theological virtues as faith, hope and charity, which is the way I’ve always heard it. In a K of C home study course, love is substituted for charity. I can see the connection, of love growing from charity, or maybe charity growing out of love. But is this substitution valid? John said God is love and love is God, so is God also charity and charity is God? It doesn’t seem right.
The words “love” and “charity” are interchangeable when used in the context of the theological virtue. Look up “love” in the catechism glossary and you’ll find: “See Charity”. Charity is defined as, “The theological virtue by which we love God above all things for his own sake, and our neighbor as ourselves for the love of God” (Catechism glossary).
See also Love (Theological Virtue).