Money Wisdom #216

"...the discovery of the common 'conservative nature' of the instincts militates against the dualistic conception and keeps Freud's late metapsychology in that state of suspense and depth which makes it one of the great intellectual ventures in the science of man. The quest for the common origin of the two basic instincts can no longer be silenced. Fenichel pointed out that Freud himself made a decisive step in this direction by assuming a 'displaceable energy, which is in itself neutral, but is able to join forces either with an erotic or with a destructive impulse' - with the life or death instinct."

Herbert Marcuse Eros and Civilization (1956 [1998]) p.28