[In "Irrational Man: A Study in Existential Philosophy"] William Barrett has presented the most thorough account yet written for the American layman of the philosophy that has attracted so much attention in Europe since World War II—Existentialism. This philosophy is a protest against the submersion of the individual in a mass society, and Mr. Barrett … shares in this protest. A man with a taste for both poetry and politics, an independently minded philosopher and a writer of vigor and passion, he believes that the intellect in the modern world has become an inhuman gadget and that organized reason has given our civilization unprecedented powers, which it uses without taste or moral insight.

The author, however, does not think that our troubles come from having failed to take reason seriously enough. They come, he believes, from having taken reason too seriously. For the belief in reason, to his...