1 John 1:6

If we say [ε α ν ε ι π ω μ ε ν]. The subjunctive mood puts the case as supposed, not as assumed.

Walk in the darkness. The phrase occurs only in John's Gospel and First Epistle. Darkness here is skotov, instead of skotia (ver. 5). See on John 1:5. Walk [π ε ρ ι π α τ ω μ ε ν], is, literally, walk about; indicating the habitual course of the life, outward and inward. The verb, with this moral sense, is common in John and Paul, and is found elsewhere only in Mark 7:5; Acts 21:21.

We lie and do not the truth. Again the combination of the positive and negative statements. See on ver. 5. The phrase to do the truth occurs only in John's Gospel and First Epistle. See on John 3:21. All walking in darkness is a not doing of the truth. "Right action is true thought realized. Every fragment of right done is so much truth made visible" (Westcott).