Definition of "authentick"

[T]here they find Ignatius, and then they believe him not for his ovvn Authority, but for a truths ſake, vvhich they derive from elſvvhere: to vvhat end then ſhould they cite him as Authentick for Epiſcopacy, vvhen they cannot knovv vvhat is Authentick in him, but by the judgment vvhich they brought vvith them, and not by any judgment vvhich they might ſafely learn from him?

1641 June or July, John Milton, Of Prelatical Episcopacy, and Whether It may be Deduc’d from the Apostolical Times by Virtue of Those Testimonies which are Alledg’d to that Purpose in Some Late Treatises; […]; republished in A Complete Collection of the Historical, Political, and Miscellaneous Works of John Milton, […], volume I, Amsterdam [actually London: s.n.], 1698, page 242