We have not sinned (ouch hamartēkamen). Perfect active indicative of hamartanō. This is a denial of any specific acts of sin, while in 1Jo 1:8 we have the denial of the principle of sin. David Smith observes that the claim to personal perfectionism has two causes, one the stifling of conscience in making God a liar (pseustēn, the word used of the devil by Jesus in Joh 8:44), and the other ignorance of God’s word, which is not in us, else we should not make such a claim.