Walking in the light is demonstrated not by the denial of sin but by confessing it and abandoning it. This action links us to God's mercy. Those who confess their sins and condemn them are linked to God. And we can confess our "sins" to God and before other people fearlessly and in confidence because God is both faithful and just.
The plural "sins" makes clear that we affirm our sinfulness by confessing our sins. The forgiveness that comes is related to God's faithfulness and justice. Everywhere he promises forgiveness to his children. And in keeping this promise, God reveals his faithfulness and justice.
The verb used for "forgive" has at its roots the idea of the "cancellation of debts" or the "dismissal of charges." The verb used for "purifies" pictures an act of cleansing from the pollution of sin so that a new life of holiness may begin. Sinners are perceived as cleansed from moral imperfections and from the injustices that separate them from God.
Forgiveness follows confession. Guilt then vanishes: Forgiveness from God comes through Christ, and such forgiveness will “cleanse our consciences from dead works.” (Col. 1:14; Heb. 9:14) Then our consciences need no longer feel guilt. So, we should face our sin, acknowledge it, confess it to God, seek forgiveness of it. Confession is followed by forgiveness and that ends the matter.