2 Corinthians 13:5 Examine yourselves, whether ye be in the faith; prove your own selves. Know ye [Greek epiginṓskō] not your own selves, how that Jesus Christ is in you, except ye be reprobates?
This verse tells us if we do not know the Lord Jesus Christ is in us, we have failed the test.
2 Corinthians 13:6 But I trust that ye shall know that we are not reprobates.
This verse tells us that Paul knew the Lord Jesus Christ was in him and, therefore, Paul had not failed the test.
in 2 Cor 13:5, the words "know ye" are translated from the Greek word epiginṓskō (from 1909 /epí, "on, fitting" which intensifies 1097 /ginṓskō, "know through personal relationship") – properly, apt, experiential knowing, through direct relationship - HELPS Word-studies.
We can know in this lifetime, beyond a shadow of a doubt, that the Lord Jesus Christ is in us ... and because the Lord Jesus Christ is in us we have eternal life ...
1 John 5:20 And we know that the Son of God is come, and hath given us an understanding, that we may know him that is true, and we are in him that is true, even in his Son Jesus Christ. This is the true God, and eternal life.
.