1 John 1:5-9 NIV
This is the message we have heard from him and declare to you: God is light; in him there is no darkness at all. If we claim to have fellowship with him and yet walk in the darkness, we lie and do not live out the truth. But if we walk in the light, as he is in the light, we have fellowship with one another, and the blood of Jesus, his Son, purifies us from all sin. If we claim to be without sin, we deceive ourselves and the truth is not in us. If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness.
There are lots of logical implications in the new testament. Read any letter written by Paul, for example, and look for the word "therefore." An important pair of implications is found in 1 John 1:
vs. 8: If we say we are without sin, [then] we deceive ourselves and the truth is not in us.
vs. 9: If we confess our sins, [then] he is faithful and just and will forgive us our sins and purify us from all unrighteousness.
Note in particular that the verse 9 implication uses the negation of the hypothesis of verse 8 as its premise. It is also interesting that the conclusion of verse 9 shifts emphasis from man to God. These two verses cover all cases in an analysis of how man responds to his relationship to sin: either you deny your sin or you confess your sin.