E4P20
Proposition — Part IV
Latin
Quo magis unusquisque suum utile quærere hoc est suum esse conservare conatur et potest eo magis virtute præditus est et contra quatenus unusquisque suum utile hoc est suum esse conservare negligit eatenus est impotens.
English (Elwes 1883)
The more every man endeavours, and is able to seek what is useful to him--in other words, to preserve his own being--the more is he endowed with virtue; on the contrary, in proportion as a man neglects to seek what is useful to him, that is, to preserve his own being, he is wanting in power.
Modern English
The more each person strives and is able to seek his own advantage — that is, to preserve his own being — the more he is endowed with virtue. Conversely, insofar as anyone neglects his own advantage — that is, neglects to preserve his own being — to that extent he is powerless.