Abstract: In this paper, I operationalize the classical retributive formulation of proportionality—lex talionis, or “an eye for an eye”— to give some conservative estimates of what it might entail as a limit on the severity of permissible punishment. Respecting lex talionis would entail a radically lenient transformation of the criminal legal systems of the United States (and many other countries), reducing incarceration for non-homicide offenses by at least an order of magnitude.