Cognitive dissonance (CD) is the concept of holding two very different ideas in your mind at the same time. This is something all the great composers do when they think of two melodic themes and how they can intertwine, adapt and combine them. We would find it very difficult to whistle one tune while thinking of an entirely different one but that is the sort of thing that Beethoven or Mozart would consider trifling.
Let us take two different ideas:
1. Man created god(s), and the concepts of soul, resurrection, afterlife, heaven & hell in Abrahamic & Reincarnation, Karma, moksha (Liberation) & ultimately heaven in Eastern religions.
2. Man wants everyday protection, eternal life & ultimate justice. All these are easily provided by a sky-daddy, if he exists.
Both these ideas are scientific facts (except for the sky-daddy clause) established by cultural anthropology and Evolutionary psychology, but it is difficult to accept both of them at the same time. It would create cognitive dissonance and unease in the common man.
To avoid CD people usually accept one and reject the other.
People tend to seek consistency in their beliefs and perceptions. So what happens when one of our beliefs conflicts with another previously held belief? The term cognitive dissonance is used to describe the feeling of discomfort that results from holding two conflicting beliefs. When there is a discrepancy between beliefs, something must change in order to eliminate or reduce the dissonance.
Some people who are science-savvy accept idea no.1, and feel that idea no.2 arose in the minds of our primitive ancestors because of the need to be safe from natural catastrophes & predators, fear of death & oblivion, and need for fair play. They feel that idea no.1 contradicts idea no.2 and hence they reject the latter and feel that they can afford to think more rationally. Such people are called Atheists.
On the other hand some others, in order to avoid CD, reject idea no.1 and accept idea no.2 as a bonus for their implicit belief & trust in supernatural entities. They are called Theists.
Then you have the third category of people who, like Mozart or Beethoven, adroitly combine the two different melodies into one symphony. Such people are basically atheistic but wish to take over the duties of an absentee caretaker, to the extent humanly possible and help others to live their lives more happily. They say seeking the truth should prevail over search for comfort. Such folks are called Secular Humanists. They have resolved their CD, without forfeiting one idea for the other.
Regarding the needs for everyday protection & justice, they would like to improve the efficacy of police & judiciary and regarding the fear of death & desire for immortality, they would like to educate people about alternative means of attaining immortality.
There are many ways of achieving immortality for non-theists:
1. Through descendance
2. Through inheritance
3. Through deeds
4. Through remembrance.
Descendance. In children and grandchildren, our genes, fused with those of our partner, live on. There is nothing quite like seeing the family resemblance in a child's face, for realizing the continuity of the generations and feeling one's embedded involvement in the process of life.
Inheritance. Almost everyone who has accumulated any degree of wealth or property likes to pass some or all of it on to their children or relatives.But even the poorest have some possessions that are unique to them- a school prize, a medal, a drawing/ painting, a diary, or some collection like a stamp collection or book collection.
Deeds. The third form of real afterlife comes about through our actions and creations whose impact persists after our death. Not only for writers and artists trying to leave immortal works behind them, but even a single act of kindness may be recollected for decades after our death.A life of loving care by some mothers will be remembered by those it touched for as long as they live. The trees we plant now will provide shade and beauty for generations.
Remembrance. Our only afterlife and immortality is in the lives and minds of those who survive us. And our only hell is in their memories, too. If we are unkind or egotistical towards other people, they won't feel sorry when we die. They may even say " good riddance ". If we hurt them seriously, they will remember us, not with love and nostalgia, but with hatred and rancor.