1 John 2:20

But ye have an unction from the Holy One, and ye know all things.

But - Greek, 'And.' He states the means which believers have to withstand Antichrists (1 John 2:18), namely, the chrism [ chrisma (G5545): a play upon similar sounds], or 'anointing unguent,' the Holy Spirit (plainly mentioned further on, in John's style, 1 John 3:24; 1 John 4:13; 1 John 5:6), which they ("ye," in contrast to those apostates, 1 John 2:19) have from Christ (John 1:33; John 3:34; John 15:26; John 16:14): "the righteous" (1 John 2:1), "pure" (1 John 3:3), "the Holy One" (Acts 3:14) "of God" (Mark 1:24). Those anointed of God in Christ alone can resist those anointed with Satan's spirit, Antichrists, who would sever them from the Father and the Son. Believers have the anointing Spirit from the Father, as well as from the Son; even as the Son is anointed therewith by the Father. Hence, the Spirit is the token that we are in the Father and in the Son; without it one is none of Christ's. The material unguent of costliest ingredients, poured on the head of priests and kings, typified this spiritual unguent, derived from Christ, the Head, to us, His members. We have no share in Jesus, except we become truly Christians, being in Christ, anointed with that unction from the Holy One. The Spirit poured on the Head is by Him diffused through the members. 'We all are the body of Christ, because we all are anointed; we all in Him are both Christ's and Christ, because in some measure the whole Christ is Head and body.'

And - therefore.

Ye know all things - needful for acting against Antichrist's seductions, and for Christian life. In whatever measure one hath the Spirit (no more and no less), he knows all needful things.