It may be doubted whether the participle (εἰδότας) is rightly rendered "_though_ ye know all things once for all." It makes good, and perhaps better sense to understand it in the equally possible signification of "_because_ ye know all things once for all." Their being already in full possession of a knowledge of Old Testament history is the reason why St. Jude need do no more than remind them of one or two particulars which throw a terrible light upon the position of those whose conduct is being discussed. That "once" here does not mean "formerly," as the Authorized Version takes it, "though ye _once knew_ this," is manifest to every one who knows the meaning of the participle and adverb here used (εἰδότας ἅπαξ). Nor is there much doubt that both here and in ver. 3 it does mean "once for all." This Greek adverb, like its Latin equivalent _semel_, is sometimes "used of what is so done as to be of perpetual validity and never need repetition." It is twice so used in the Epistle to the Hebrews: "For as touching those who were _once_ enlightened and tasted of the heavenly gift" (vi. 4); _i.e._ once for all enlightened, so that no second enlightenment is possible. And again, "Because the worshippers, having been _once_ cleansed, would have had no more conscience of sins" (x. 2). So also in 1 Peter: "Because Christ also died for sins _once_" (iii. 18). The meaning is similar in both the passages here (vv. 3 and 5). The Gospel was once for all delivered by the Apostles to the Church; for there can be no second Gospel. And this Gospel Christians receive and know once for all.