Orthodoxy regards sin simply as "separation from God." In fact, the Greek term is "missing the mark" (the "mark" being Christ); when God is not our mark, we sin. As long as our aim is to imitate Christ, as long as we are in communion with Him, we don't. That's where the idea of frequent confession and communion comes from.
Is there a need for God to forgive sin?
God neither has needs, nor is He driven by necessities. If we follow Christ, we will feel a need to confess our sins, not as a legalistic obligation, but as a realization that we have been ungrateful to Him.
Confession is not a true confession unless it is grounded in what the Greeks call metanoia (change of mind), a permanent and irrevocable rejection of that which we confessed as our ingratitude to God. We believe that God forgives us if our ingratitude is an honest failure and our confession an honest desire to change our mind. God will forgive if we honestly try, even if we honestly fail.
"Deification" implies an idea to me of becoming "as a God", or "equal to God"
Oh, no, never equal to God! That would be pagan. Theosis is becoming God-like, Christ-like. It is a process, a spiritual growth to holiness through faith in God, in due time. The "official" Saints reached that likeness to God more than your average bear. They have achieved that by denial of their passions and carnal qualities of our fallen nature, and incessant prayers. They became empty vessels, "poor in spirit," without egos, clean glasses, through which the light of God could shine for others to see and know Him.
People who achieve theosis don't know it. Their humility does not allow them to arrogate such quality. They consider themselves truly unworthy of any honor or title. In fact, they are truly disconcerned with such things as honors and titles, or anything of this world for that matter. :-)
God neither has needs, nor is He driven by necessities. If we follow Christ, we will feel a need to confess our sins, not as a legalistic obligation, but as a realization that we have been ungrateful to Him.
I'm sorry, I meant is there a need by man to be forgiven of sin by God for salvation? I thought I remembered that actually achieving theosis is rare for someone, at least in this lifetime, but that it was still possible to be saved. I was trying to ask how integral is God's forgiveness of sins to this? I guess I mean is God's forgiving of our sins one piece of a larger salvation puzzle, or is it absolutely key?
Theosis is becoming God-like, Christ-like. It is a process, a spiritual growth to holiness through faith in God, in due time.
You may have heard people of my faith say things like they want to adopt "the mind of Christ" or that we should "conform ourselves to the image of Christ". Are these comparable? Also, theosis sounds a lot to me like what I would call sanctification. Is this right, or are there important differences?