Jamieson, Fausset & Brown

For--literally, "Since," seeing that. This verse illustrates how the "preaching" of Christ crucified came to be deemed "foolishness" (Co1 1:21). a sign--The oldest manuscripts read "signs." The singular was a later correction from Mat 12:38; Mat 16:1; Joh 2:18. The signs the Jews craved for were not mere miracles, but direct tokens from heaven that Jesus was Messiah (Luk 11:16). Greeks seek . . . wisdom--namely, a philosophic demonstration of Christianity. Whereas Christ, instead of demonstrative proof, demands faith on the ground of His word, and of a reasonable amount of evidence that the alleged revelation is His word. Christianity begins not with solving intellectual difficulties, but with satisfying the heart that longs for forgiveness. Hence not the refined Greeks, but the theocratic Jews were the chosen organ for propagating revelation. Again, intellectual Athens (Act 17:18-21, &c.) received the Gospel less readily than commercial Corinth.