The lucidity of thought and expression in this work by the greatest living French philosopher is a refreshing experience in the welter of books on this very problem of ideas, viz: how the mind achieves universality or generality, in other words unifies the multiple data outside the mind. This problem with its solution is admirably set forth and the historical attempts to solve it are criticized with eminent fairness. Even those who cannot call themselves realists as Gilson, will find delightful intellectual satisfaction in the book. We are tempted to think that if its title were not so technical, it would achieve some of the success of a best-seller, such as Dimnet's book on The Art of Thinking, because it has none of the pretensions of a technical discussion, and far more depth than the bulk of such discussions.