Justice is double; punishing with severity, preventing with lenity.

Explanation

The two arms of justice are punishment after the fact and prevention before it — the law is most effective when it deters wrongs before they occur through gentle warning, reserving harsh measures for those who offend nonetheless.

Where this applies

• It's better to warn people away from crime than to punish them after they commit it.
• Prevention through education and deterrence is preferable to harsh punishment after the fact.