Scien meaning

1851: John Mitford, The works of John Milton in verse and prose, printed from the original editions with a life of the author by the Rev. John Mitford, volume VIII (Prose works, volume VI), § 3 : “ Letters written in the Name of Oliver The Protector,” page 404 〃 〃 〃 〃 (London : William Pickering)

It ſeems to be only in your Power, next under God, to prevent the extirpation of this moſt antient Scien of the purer Religion, in theſe remainders of the Primitive Believers; whoſe preſervation, now reduc’d to the very brink of utter ruin, if you neglect, beware that the next Turn be not your own.