Thomas Erastus (September 7, 1524 – December 31, 1583) was a Swiss physician and theologian. He wrote 100 theses (later 75) in which he argued that the sins committed by Christians should be punished by the State, and that the Church should not withhold Sacraments as a form of punishment. They were published in 1589, after his death, with the title Explicatio gravissimae quaestionis. Swiss physician and religious controversialist whose name is preserved in Erastianism, a doctrine of church-state relationship that he himself never taught.