“ For every bad man is not bad only when he breaks out into crime, but he has the seeds of vice in his nature, and is only vicious in act when he has opportunity and means, as opportunity makes the thief steal,861 and the tyrant violate the laws. ”
 Plutarch, Moralia (c. 100 AD). copy citation

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“whereas mankind, under the influence of customs and opinions and laws, frequently conceal their bad qualities and imitate what is good, so as altogether to obliterate and escape from the innate taint of vice, or to be undetected for a long time, throwing the veil of craft round their real nature, so that we are scarce conscious of their villainy till we feel the blow or smart of some unjust action, so that we are in fact only aware that there is such a thing as injustice when men act unjustly, or as vice when men act viciously, or as cowardice when men run away, just as if one were to suppose that scorpions had a sting only when they stung us, or that vipers were venomous only when they bit us, which would be a very silly idea. For every bad man is not bad only when he breaks out into crime, but he has the seeds of vice in his nature, and is only vicious in act when he has opportunity and means, as opportunity makes the thief steal,861 and the tyrant violate the laws. But the deity is 356not ignorant of the nature and disposition of every man, inasmuch as by his very nature he can read the soul better than the body, and does not wait to punish violence in the act, or shamelessness in the tongue, or lasciviousness in the members.” source