From a defense of incidental plagiarism....

     We, as human beings, are landed with memories which have fallibilities, frailties, and imperfections—but also great flexibility and creativity.  Confusion over sources or indifference to them can be a paradoxical strength:  if we could tag the sources of all our knowledge, we would be overwhelmed with often irrelevant information.  Indifference to source allows us to assimilate what we read, what we are told, what others say and thing and write and paint, as intensely and richly as if they were primary experiences.  It allows us to see and hear with other eyes and ears, to enter into other minds, to assimilate the art and science and religion of the whole culture, to enter into and contribute to the common mind.  Memory arises not only from experience but from the intercourse of many minds.

-Oliver Sacks,  The River Of Consciousness, from the chapter The Fallibility of Memory