Reincarnation and past lives have been very popular themes in science fiction and fantasy. The collective unconscious, as formulated by the psychotherapist Carl Jung, though less immediately understandable and less famous, has also been used as the basis for very interesting fiction.

The collective unconscious was one of Carl Jung’s most influential theories; it consists essentially of inherited memories shared by all human beings that go back countless generations into prehistory.

JG Ballard’s novel “The Drowned World” takes the idea of the collective unconscious right back to the Triassic period many millions of years ago. The loss of individual identity for many of the human protagonists is an important aspect of the novel; they live increasingly in memories of a primordial world that extend back ultimately to their non-human ancestors in the Triassic.

In an essay, Ballard suggests that the landscapes encountered in surrealist painters like Dalì, De Chirico and Ernst, so often described as “dream-like”, do not really resemble ordinary dreams. Instead, they are representations of primordial memories that we all have and which certain people like those artists are able to express at certain times.

Jung tried to reconcile his theory of the collective unconscious with that of reincarnation or metempsychosis, according to which each person has had many previous lives; the karma accumulated in a previous life determines the person’s next life. Jung claimed that karma could be either personal or impersonal; he even stated that the Buddha had not specified which of these was correct. However, Jung seems clearly wrong in this; karma is always personal.

Jung’s attempt to reconcile the predominantly eastern belief in personal karma with his own theory of the collective unconscious has its logic, despite Jung’s lack of understanding of karma.

If karma could be impersonal, as he claimed, then the memories of past lives that many people claim to have is readily explicable; these memories derive from the collective unconscious. The experience is real but the common explanation (“I have lived before”) is wrong; it would be more correct to say that “someone has lived before, but not me”.

Jack London’s novella “Before Adam” specifically refers early on to the reincarnation versus collective unconscious question. The narratorial voice states that reincarnation is not true, although the subjects believe they have lived before; what they have really experienced is memories from the collective unconscious.

Jung’s idea of impersonal karma would allow an interpretation of reincarnation that would be palatable to mainstream western thought, where reincarnation has not been a standard view since the time of Plato and Pythagoras more than 2,000 years ago. Nevertheless, the necessity for karma to be personal means that the mainstream views of east and west on this point remain far apart.