Doctor Who: The Five Doctors has two principal themes: the definition of the individual and the quest for eternal life.

Neither theme is worked out in depth, but both are important for understanding the characters' motivations.

When Doctor Five's previous selves are wrenched out of time and space, he says, "I am being diminished. Whittled away, piece by piece. ... A man is the sum of his memories, you know, and a Time Lord even more so." All five versions of the Doctor face the same problem: the tearing apart of their identity as the Doctor, and death by the loss of the memories each incarnation represents.

A madman who seeks eternal life has put the Doctor into this dangerous predicament. Once a good if somewhat hidebound leader of the Time Lords, Borusa has become convinced that he is indispensable to the Time Lords. His...