You feel a sudden flash of resentment at someone else's good fortune and want to check whether it's a real injustice or envy dressing up as principle.

Satan watches Adam and Eve — "sight hateful, sight tormenting!" — and converts envy into an argument. The one rule, one forbidden tree, becomes "knowledge forbidden, suspicious, reasonless"; the master's rule is reframed as the master's insecurity, "invented with design to keep them low." This is the exact pitch he will later make to Eve. Dress envy as emancipation and the target will do the destruction for you.