Who is the liar but he who denies that Jesus is the Christ? This is the Antichrist, he who denies the Father and the Son.

 We do not say that there is no thought of age groups in this. There almost certainly is; but John has a way of saying things which can be taken in two ways, a narrower and a wider; and, while the narrower meaning is here, we must go beyond it to find the full meaning. 