All cruelty springs from weakness.
Info & reflection: The sentence turns a common assumption around: cruelty is not a sign of strength but of its absence. Whoever harms others acts out of fear, insecurity or lack of self-control, not from a position of real power. In Seneca's Stoic frame, true strength is self-mastery: someone who is really strong has no need to dominate or to cause pain. The tyrant, the bully, the one who humiliates: they act out of unresolved anxiety and a fragility they can't handle any other way.
Note: There is also the variant "all savageness is a sign of weakness", another translation of the same idea. The exact English wording is a modern rendering of the Latin original.
Related in anthology
- Nothing, however, will help you so much as keeping still—talking very little with others, and as much as may be with yourself. — the inner dialogue Seneca prescribes is the practice that builds the self-mastery whose absence is cruelty