The shape of the cross, as represented by the letter T, came to be used as a "seal" or symbol of Early Christianity by the 2nd century. At the end of the 2nd century, it is mentioned in the Octavius of Minucius Felix, rejecting the claim by detractors that Christians worship the cross. The cross (crucifix, Greek stauros) in this period was represented by the letter T. Clement of Alexandria in the early 3rd century calls it τὸ κυριακὸν σημεῖον ("the Lord's sign") and he repeats the idea, curren…