Two months before his death, in a ceremony at the White House, Norbert Wiener was awarded the National Medal of Science. The citation by President Johnson said: " . . . for marvelously versatile contributions, profoundly original, ranging within pure and applied mathematics, and penetrating boldly into the engineering and biological sciences." Our assignment here is twofold: we want to explore how Wiener came to penetrate into biology, a field into which few real mathematicians had strayed before him; we should also like to assess, no matter how incompletely, the imprint that Wiener has left upon the sciences of Life and Man. From his early youth Wiener, the prodigy, acquired intensive experience in the manipulation of both mathematical and linguistic symbols; but his career choice seemed initially little related to these skills. Perhaps in part due to his father's acquaintance with Walter B. Cannon, Norbert seemed sufficiently interested in biology to become a graduate student in zoology at Harvard University, after he had graduated at the age of 14 from Tufts College. But, in spite of his interest in the subject matter, Norbert had neither the manual skill nor the patience to do well in the graduate courses in biology of that era. In one of his autobiographical books Wiener commented on the contrast between his quick insight into ideas and his extreme lack of manual dexterity as follows: "This impatience was largely the result of a combination of my mental quickness and physical slowness. I would see the end to be accomplished long before I could labor through the manipulative stages that were to bring me there. When scientific work consists in meticulously careful and precise manipulation which is always to be accompanied by a neat record of progress, both written and graphical, impatience is a real handicap. How much of a handicap this syndrome of clumsiness was I could not know until I had tried. I had moved into biology, not because it corresponded with what I knew I could do, but because it corresponded with what I wanted to do. "It was inevitable that those about me discouraged me from further work in zoology and all other sciences of experiment and observation. Nevertheless, I have subsequently done effective work together with physiologists and other laboratory scientists who are better experimenters than I, and I have made some definite contributions to modern physiological worker" After a short period as a "philosopher despite himself," Wiener found his way into mathematics via a doctoral dissertation in the area of Russellian logic, and a few "Wander"-semesters at Cambridge (on the Cam) and Gottingen. The involvement of America in World War I brought Norbert Wiener to the Aberdeen Proving Grounds and involved him in the computation of ballistic tables. After a short and not too happy interlude as a journalist, Wiener joined the Massachusetts Institute of Technology Mathematics Department in 1919. Although during the next 45 years Wiener remained a productive member of this Department, he had an important influence in many other departments of the Institute as well. Few are the fields of science, engineering, social science or even humanistic scholarship which Wiener's thoughts failed to stir up, often in a rather unorthodox manner. Wiener's presence at M.I.T. spans the period during which the Institute transformed itself from a technical school into a university of a novel type, one apolarized around science," and his intellectual virtuosity, curiosity and integrity contributed importantly to that transition. When Wiener came to M.I.T., the Mathematics Department was predominantly a service department concerned with preparing students for engineering careers. In a manner which more pure mathematicians in the United States could emulate, Wiener did not hesitate to become interested in the problems of his engineering colleagues. When many years later the great English mathematician, Hardy, claimed that Wiener's engineering terminology was mere camouflage, he misunderstood both Wiener's motivations and sense of social responsibility. Even the purest of mathematics can be a potent tool in very practical pursuits, and Wiener felt that mathematicians, to be effective, need to realize that their labors are changing the nature of society. Most of Wiener's later mathematical work stemmed from his early interest in the study of irregularities and in his attempts to give meaningful mathematical descriptions of such irregularities, no matter where in nature they occur. His study of Brownian motion led him to study forms of harmonic analysis more general than the classical Fourier series and the Fourier integral. He developed both auto- and cross-correlation analysis and related them to the established forms of spectral analysis.