Relating to the doctrine that the state should have supreme authority over the church in religious matters.
From Thomas Erastus (1524-1583), a Swiss theologian who argued for state control of ecclesiastical affairs. The '-ian' suffix indicates the doctrine or belief system named after him, though Erastus himself did not fully advocate this position.
The irony is that Thomas Erastus didn't actually believe what 'Erastians' believe—his name got attached to a position he only partly held, making 'Erastian' one of history's great examples of a word that means something different from what its namesake actually thought!
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