The literary and philosophical movement known as existentialism receives passing mention in Barfield's writings, primarily as an exemplary consciousness soul mind-set. In Saving the Appearances, for example, he offers his own reading of existentialism's most famous tenet.
Man, said J. P. Sartre, is a being who is condemned to freedom. That is one way of looking at it. And it is the only way, if man himself is nothing but a hollow idol. But if man is not hollow, but is the theatre on which participation has died to rise again, then there is also another way of looking at it. (185)
In Worlds Apart he notes that the movement is as guilty of double think as most of modern thought: "[The existentialists] claim that man is responsible for all that exists, and yet the creature that bears this responsibility is for them a hollow void" (WA 180).
See in particular Worlds Apart, passim.