P22: No virtue can be conceived prior to this {virtue} (viz. the striving to preserve oneself).

Dem.: The striving to preserve itself is the very essence of a thing (by IIIP7). Therefore, if some virtue could be conceived prior to this {virtue}, viz. to this striving, the very essence of the thing would be conceived prior to itself (by D8), which is absurd (as is known through itself). Therefore, no virtue, etc., q.e.d.

Cor.: The striving to preserve oneself is the first and only foundation of virtue. For no other principle can be conceived prior to this one (by P22) and no virtue can be conceived without it (by P21).