1. Denial - In this stage the believer is confronted with facts that attacks both the credibility of the so-called “truths of the Bible" and the Christian faith. Here the believer often counters with apologetically programmed or canned responses.
2. Anger - The individual recognizes that denial cannot continue as he or she becomes frustrated, being unable to reconcile logical reality with theology and faith. Without the truth of the Bible supporting theology, the Christian faith begins to deconstruct itself.
3. Bargaining – In this stage, the believer may move to a more liberal Biblical interpretation that seems easier to defend hoping that God’s truth might be better understood though the use of allegory and not Biblical literalism which now seems to have more in common with myth. It is at this stage the believer tries to reformulate both God and theology by claiming that he or she just didn’t understand who or what God really is.
Christians depending on allegory in this stage (as well as neo-apologists who I term religious atheists) often label completed atheists (those who have been though stages 1 & 2 above) Fundi-atheists.
4. Depression - At this stage, the whole Christian theological system is viewed as a fraud and God as nothing more than a construct of faith and theology forced on others by believers, who were (in turn), manipulated by (paid) professional ministers. It is at this stage one often feels hopeless and deceived since their sincere honesty failed to bring the promised absolute truth from God. Now the struggling believer seeks answers as to why they simply took things on faith and didn’t ask more objective questions. It is at this point they are usually cut off from Christian fellowship (shunned) before being told to repent.
5. Acceptance - In this final stage, the former Christian realized he or she never was a “sinner”, but fell for a theological scheme that preyed upon their mental state at a time of need or by religious coercion (Confirmation). At this time the former believer realizes the theological system of faith that claimed to have all the answers about life and eternity really had none. Now the post-religious believer must construct new morals and ethics in context with modern science as he or she works in a new secular light to understand the world and the universe around them.
(As noted by Kübler-Ross (on whose work my post is based), these stages may not necessarily come in the above order, nor are all stages experienced by all atheists. These five stages are based on Swiss psychiatrist Elisabeth Kübler-Ross in her 1969 book, On Death and Dying, via her work with terminally ill patients.)
The above post is a reworking of my 2013 post entitled, Stages of Losing Faith: