The title of [What Is Existentialism?] would lead one to expect a pedestrian but systematic introduction to the subject of the sort usually addressed in the preface "to the general reader" or to "the educated public"—but which normally mystifies and rarely educates. Happily, the title is deceptive. This volume is neither a systematic treatment nor one which deals with existentialism in general. It offers instead two essays, related and partly overlapping, on the thought of one philosopher, Martin Heidegger. Moreover, these two essays, the composition of which was separated by "more than a dozen years," represent the author's attempt, not to popularize, but to divine the significance of Heidegger's thought as an event in the history of philosophy.
But in the end Mr. Barrett's accomplishment of this task does constitute, in a way, a highly successful introduction to existentialism; indeed, this is one of the best secondary sources yet available in English on the subject. The reason is that Mr. Barrett is one of the relatively few English-speaking philosophers who has attempted to view the contemporaneity of existentialism not as a novel or bizarre phenomenon, but as a historically present reality. The author, therefore, is far removed from that legion who, with the unquestionable but lifeless expertise of a Thomas Langan, dissect existentialism as if it were an unidentified body washed up to our domestic shores…. Mr. Barrett conveys the more important truth that existentialism is not simply an interesting episode in the annals of recent academic fads, but the conceptualization and intellectualization of a culture-wide phenomenon, deeply rooted in the history of the Western mind, and sufficiently pervasive and powerful to warrant recognition as the philosophical type which manifests the thermonuclear age.
Understandably, Mr. Barrett achieves this less aptly in the earlier of his two essays than in the second. For apparently it was only gradually, as the author studied "the later Heidegger," that he discovered what is perhaps one of the central points of Heidegger's philosophical contribution to the development of the human mind: "the history of philosophy, for Heidegger, is not isolated from the rest of human history. On the contrary, it is human history brought to its fullest revelation, so that what happens in philosophy is prophetic of what is to happen later in the rest of man's social and political life. Heidegger's interpretation of the history of philosophy thus entails a very definite interpretation of the whole history of Western civilization …".
The same "positioning" of Heidegger's thought as a philosophy of history which is itself a historical, cultural event, enables Mr. Barrett to explain more satisfactorily than most critics do the relation of Heidegger to modern literature and art, and his profound interest in poetry at a certain stage of his development as well as his life-long preoccupation with language. (p. 23)
More important, Barrett shows that "the theme of history is central to the later Heidegger, and whatever he attempts to interpret—whether it be poetry, the meaning of technology, or a pre-Socratic philosopher—is understood within his own bold and simple scheme for Western history as a whole." However, it must be remarked that "all, or nearly all, the details" in Heidegger's interpretation of contemporary times in philosophical terms "are commonplace matters."… But, if so, in what consists Heidegger's originality? It consists "in the way he sees this fact as embedded within the whole history of Western philosophy. This historical vision is granted him because he takes philosophy itself as a central and decisive fact within Western history. The great philosophers are not merely idle speculators whose ideas may happen, in some passive way or other, to reflect the changes that are going on in the substratum of history; on the contrary, these philosophers project the future by laying down certain schemata of thought within the framework of which subsequent history plays out the details." This original interpretation, lucidly and convincingly defended, is Mr. Barrett's notable contribution to the literature on the subject. (pp. 23-4)
Leslie Dewart, "Historical Vision," in The Canadian Forum, Vol, XLV, April, 1965, pp. 23-4.