On Sin

“THERE are two sides to every sin, the turning to transient satisfaction and the turning away from everlasting value. As regards the first, the principle of all sins can be called lust—lust in its most general sense, namely, the unbridled desire for one’s pleasure.  As regards the second, the principle is pride, pride in its general sense, the lack of submission to God.” (Disputations concerning Evil, 8, 1.)

“PRIDE strives for perverse excellence, a very special sin when God is despised, but also present whenever our neighbor is despised.”  (Disputations concerning Evil, 8, 2.)

~St. Thomas Aquinas

See also, "The cause of sin, in respect of one sin being the cause of another": ST, I-II, q. 84.

The Seven Deadly Sins and The Four Last Things, by Hieronymus Bosch.
Oil on panel, c. 1480; Museo del Prado, Madrid.