People usually think that the whole point of memory, especially that of episodes, is in the fact that it can be explicitly recalled. Unremembered memories seems to be a contradiction in definition, or at least useless. However, it is a fact that unremembered memories are important ingredients of our life, something we cannot really do without.
Think of, for example, what explicit memories you have from your childhood, in relation to your parents. You have spent endless hours of life with your mother and father, and yet, it is not easy to explicitly remember specific incidents and occurrences, especially as you go back in life to your infancy. The sentiment towards your parents, the idea of "mother" or "father" that is conjured up within you when thinking of them, is genuinely a product of these unremembered memories. The fact that you cannot "remember" all these episodes from the time you spent with your parents does not mean that in the brain there isn't this rich layer of records of your life under the care of well meaning adults in a past now so distant.
I had a striking personal experience concerning the significance of unremembered memories myself. For a while, I heard repeatedly the name "Shigeo Miki", an anatomist who taught at the Tokyo National University of Fine Arts and Music. People spoke of Miki with reverence, and I was very much interested in his idea that during fetal development the history of the evolution of live is virtually repeated. Miki's idea about "life memory" had a strong influence on many people. The eloquence of his lectures was a live and growing legend.
I, however, was under the impression that I had never been blessed by his speech or his writings. I somehow had not read any of his books, and when people spoke of Miki, it was felt as if he was somebody in the distance, glowing with intellect and wisdom but thus far not having much to do with my own life. And I felt it was too late. He had long passed away.
Then one day, I realized with a shock that I actually attended one of his lectures once. I was still early 20 something, studying Physics as an undergraduate in University of Tokyo. I was walking in the campus with my girl friend, and we accidentally noticed a poster depicting a human fetus. We were greatly interested and walked straight into the lecture room.
The room was packed with people, there were not seats available, and we stood at the very back of the auditorium. The light went out and we were enclosed in gentle darkness. The speaker showed a series of photos of the fetus in development, and discussed how the whole history of life's evolution is repeated in the organic development that kick-starts every one of our own lives.
I do not explicitly recall the details of his speech, but I faintly remember that I was very moved. When the talk was over, there was a thunder of applause.
My girl friend had been standing beside me during the lecture. When the light came back, I realized that the left part of my jacket was wet. I took a look and realized that it was the tears of my girlfriend, who had buried her face in my breast.
We went out of the lecture room into the fresh air of late spring. As we walked, I asked my girl friend what made her cry. She answered that the lecture convinced her that human life is very valuable. She then added.
"Yet, we continue to kill each other in the war. Why?".
That was then. Almost 20 years passed, my girl friend's and my own life went into different trajectories, and I somehow did not recall the incident for a long time. Then one day, I suddenly remembered the lecture on that day and realized that it must have been given by Shigeo Miki himself. I was strangely convinced the moment I remembered it.
I went around checking. I asked the art critic Hideto Fuse, who was a disciple of Miki whether Miki ever gave a lecture in University of Tokyo. Hideto answered yes. Miki talked twice. It appeared that I attended the second lecture, the last lecture Miki gave in University of Tokyo, before his death a few years later.
The whole episode shook my world view from the deep root. All these years during which I was not aware that I had attended Miki's lecture once, I was without knowing under the influence of his thoughts. Once, as I was watching the waves on a beach in the island of Bali, Indonesia, I was thinking of the long history of life forms as they evolved in the sea and slowly made it to the land. I was contemplating the significance of our own existence, and I thought I was doing it on my own. Actually, my whole thoughts were under the influence of Shigeo Miki, unaware of it though I was.
Thus, memories that are not explicitly recalled play an important role in life. Our spiritual life is made of unremembered memories.