is good, and is considered part of God's plan for humanity. However, when sexual desire is separated from God's love, it becomes disordered and self-seeking. This is seen as lust.

St. Thomas Aquinas differentiates between sexual intercourse within marriage, which is seen as meritorious through giving justice to one's spouse, and sins of lust which can themselves be differentiated in magnitude of immorality according to intention and action. For example, Aquinas says in the Summa Theologica