Whitehead's grandfather Thomas Whitehead was a self-made man who started a successful boys' school known as Chatham House Academy. His father, Alfred Whitehead, an Anglican clergyman, in turn headed the school and later became vicar of St. Peter's in Thanet. His mother, born Maria Sarah Buckmaster, was the daughter of a prosperous military tailor. Alfred North Whitehead was their youngest child. Because they considered him too frail for school or active sports, his father taught him at home until he was 14, when he was sent to Sherborne School, Dorset, which was then one of the best schools in England. Whitehead received a classical education, showing a special gift for mathematics. Despite his over-protected childhood, he showed himself a natural leader. In his last year at school, he was head prefect, responsible for all discipline outside the classroom, and was a highly successful captain of games.

In 1880 Whitehead entered Trinity College, Cambridge (Cambridge, University of), on a scholarship. He attended only mathematical lectures, and his interests in literature, religion, philosophy, and politics were nourished solely by conversation. It was not until May 1884, however, that he was elected to an elite discussion society known as the “Apostles.” Whitehead did well in the Mathematical Tripos (honours examination) of 1883–84, won a Trinity fellowship, and was appointed to the mathematical staff of the college. His interest in James Clerk Maxwell's theory of electricity and magnetism (the subject of his fellowship dissertation) expanded toward a scrutiny of mathematical symbolism and ideas. Stimulated by pioneering works in modern algebra, he envisaged a detailed comparative study of systems of symbolic reasoning allied to ordinary algebra. He did not begin to write his Treatise on Universal Algebra (1898), however, until January 1891, one month after his marriage to Evelyn Willoughby Wade. She had been born in France, a child of impoverished Irish landed gentry, and educated in a convent. She was a woman with a great sense of drama and a real and unusual aesthetic sensibility, and she enriched Whitehead's life immensely.

Shortly before his marriage, his long-standing interest in religion had taken a new turn. His background had been solidly tied into the Church of England; his father and uncles had been ordained; so had his brother Henry, who would become bishop of Madras. But Whitehead, under the influence of Cardinal Newman, began to consider the tenets of the Roman Catholic Church. For about eight years he read a great deal of theology. Then he sold his theological library and gave up religion. This agnosticism did not survive World War I, but Whitehead was never again a member of any church.

Whitehead was at work on a second volume of his Universal Algebra from 1898 to 1903, when he abandoned it because he was busy on a related, large investigation with Bertrand Russell (Russell, Bertrand). He had spotted young Russell's brilliance when he examined him for entrance scholarships at Trinity College. In 1890 Russell was a freshman studying mathematics there, and Whitehead was one of his teachers. Gradually the two men became close friends. In July 1900 they went to the First International Congress of Philosophy in Paris, where they were impressed by the precision with which the mathematician Giuseppe Peano (Peano, Giuseppe) used symbolic logic to clarify the foundations of arithmetic. Russell at once mastered Peano's notation and extended his methods. By the end of 1900 he had written the first draft of his brilliant Principles of Mathematics (1903). Whitehead agreed with its main thesis—that all pure mathematics follows from a reformed formal logic so that, of the two, logic is the fundamental discipline. By 1901 Russell had secured his collaboration on volume 2 of the Principles, in which this thesis was to be established by strict symbolic reasoning. The task turned out to be enormous. Their work had to be made independent of Russell's book; they called it Principia Mathematica. The project occupied them until 1910, when the first of its three volumes was published. The “official” text was written in a notation, most of which was either taken from Peano or invented by Whitehead. Broadly speaking, Whitehead left the philosophical problems—notably the devising of a theory of logical types—to Russell; and Russell, who had no teaching duties, actually wrote out most of the book. But the collaboration was thorough, and Russell gave Whitehead an equal share of the credit. Whitehead's only large published piece employing the symbolism of the Principia is a masterly speculative memoir, “On Mathematical Concepts of the Material World” (1905).

In 1903 Trinity College had given Whitehead a 10-year appointment as a senior lecturer, made him the head of the mathematics staff, and permitted his teaching career to run beyond the maximum of 25 years set by the college statutes. Yet Whitehead's future was uncertain: he had not made the sort of discoveries that cause a man to be counted an outstanding mathematician. (His interest was always philosophical, in that it was directed more toward grasping the nature of mathematics in its widest aspects and organizing its ideas than toward discovering new theorems.) There was, thus, little prospect of a Cambridge professorship in mathematics for him at the expiration of his Trinity lectureship. He did not wait for it to expire but moved to London in 1910, even though he had no position waiting for him there. His years of service at Trinity, however, had made him a fellow for life, entitled to twice the regular quarterly dividend paid to fellows. This was scarcely enough to support his family, but Evelyn Whitehead encouraged the venture.

In that first London year, Whitehead wrote the first of his books for a wide audience, An Introduction to Mathematics (1911), still one of the best books of its kind. In 1911 he was appointed to the staff of University College (London), and in 1914 he became professor of applied mathematics at the Imperial College of Science and Technology.

In London Whitehead observed the education (education, philosophy of) then being offered to the English masses. His own teaching had always elicited his pupils' latent abilities to the fullest. Perceiving that mathematics was being taught as a disconnected set of largely unfathomed exercises, Whitehead made occasional addresses on the teaching of mathematics. He stressed getting a living understanding of a few interrelated abstract ideas by using them in a variety of ways so as to develop an intimate sense for their power. Whitehead also perceived that literature was so taught as to preclude its enjoyment, that curricula were fragmented, and that teachers were handcuffed by the system of uniform examinations set by outside examiners. In 1916, as president of the Mathematical Association, he delivered the notable address “The Aims of Education: A Plea for Reform.” Whitehead reminded youth's keepers that the purpose of education was not to pack knowledge into the pupils but to stimulate and guide their self-development. “Culture,” he said, “is activity of thought, and receptiveness to beauty and humane feeling. Scraps of information have nothing to do with it.” Whitehead's address became a classic in virtue of its unequalled clarity, vigour, and realism and its reconciliation of general with special education. It was followed by penetrating essays on such topics as the rhythm of freedom and discipline. Though Whitehead's essays on education had little effect on British practice, they inspired many teachers in Great Britain, the United States, and elsewhere.

From 1919 to 1924 Whitehead was chairman of the governing body of Goldsmiths' College, London, one of England's major institutes for training teachers. He also served as a governor of several polytechnic schools in London. In the University of London he became a member of the Senate, chairman of the Academic Council, and dean of the Faculty of Science. His shrewdness, common sense, and goodwill put him in great demand as a committeeman.

Whitehead was a pacific man but not a pacifist; he felt that the war was hideous but that England's part in it was necessary. His elder son, North, fought throughout the war, and his daughter, Jessie, worked in the Foreign Office. In 1918 his younger son, Eric, was killed in action, and after that it was only by immense effort that Whitehead could go on working. To Whitehead, Russell's pacifism was simplistic; yet he visited him in prison, remained his friend, and, as Russell later said, showed him greater tolerance than he could return.

During those years, Whitehead was also constructing philosophical foundations for physics. He was led to this by the way in which he wanted to present geometry—not as deduced from hypothetical premises about assumed though imperceptible entities (e.g., points) but as the science of actual space, which is a complex of relations between extended things. From perceivable elements and relations, he logically constructed entities that are related to each other just as points are in geometry. That was only the beginning of his task, for Albert Einstein had revised the ideas of space, time, and motion. Whitehead was convinced that these three concepts should be based upon the general character of men's perception of the external world. In 1919 he published his Enquiry Concerning the Principles of Natural Knowledge; it was both searching and constructive but too philosophical and too complicated to influence physicists.

Whitehead had begun to have discussions of the perceptual basis of scientific knowledge with philosophers in 1915, and he followed up his Enquiry with a nonmathematical book, The Concept of Nature (1920). Though he rejected Idealistic views of the relation of nature to perceiving minds, neither was he a Realist of the school led by Russell and G.E. Moore. In maintaining that events (event) are the basic components of nature and that passage, or creative advance, is its most fundamental feature—doctrines that foreshadowed his later metaphysics—Whitehead was somewhat influenced by Henri Bergson's antimechanistic philosophy of change. Yet he was something of a Platonist; he saw the definite character of events as due to the “ingression” of timeless entities.

In the early 1920s Whitehead was clearly the most distinguished philosopher of science writing in English. When a friend of Harvard University, the historical scholar Henry Osborn Taylor, pledged the money for his salary, Harvard early in 1924 offered Whitehead a five-year appointment as professor of philosophy. He was 63 years old, with at most two more years to go in the Imperial College. The idea of teaching philosophy appealed to him, and his wife wholeheartedly concurred in the move. Harvard soon found that it had acquired more than a philosopher of science; it had acquired a metaphysician (metaphysics), one comparable in stature to Gottfried Leibniz and Georg Hegel.

Early in 1925, he gave a course of eight lectures in Boston, published that same year (with additions—among them his earliest writing about God) as Science and the Modern World. In it he dramatically described what had long engaged his meditation; namely, the rise, triumph, and impact of “scientific Materialism” (Materialism)—i.e., the view that nature consists of nothing else but matter in motion, or a flux of purely physical energy. He criticized this Materialism as mistaking an abstract system of mathematical physics for the concrete reality of nature. Whitehead's mind was at home with such abstractions, and he saw them as real discoveries, not intellectual inventions; but his sense for the fullness of existence led him to urge upon philosophy the task of making good their omissions by reverting to the variety of concrete experience and then framing broader ideas. The importance of this book was immediately recognized. What perhaps impressed most readers was Whitehead's appeal to his favourite poets, William Wordsworth and Percy Bysshe Shelley, against the exclusion of values from nature.

In 1926, the compact book Religion in the Making appeared. In it, Whitehead interpreted religion as reaching its deepest level in humanity's solitude, that is, as an attitude of the individual toward the universe rather than as a social phenomenon.

In January 1927 the University of Edinburgh invited him to give a set of 10 Gifford Lectures in the ensuing academic year. For this, Whitehead drew up the complex technical structure of “the philosophy of organism” (as he called his metaphysics) and thought through his agreements and disagreements with some of the great European philosophers. It was characteristic of him to insist, against David Hume, that an adequate philosophical theory must build on “practice” and not be supplemented by it. The lectures reflected Whitehead's speculative hypothesis that the universe consists entirely of becomings, each of them a process of appropriating and integrating the infinity of items (“reality”) provided by the antecedent universe and by God (the abiding source of novel possibilities). When, in June 1928, the time for delivering the lectures arrived and Whitehead presented this system in its new and difficult terminology, his audience rapidly vanished, but the publication of the lectures, expanded to 25 chapters, gave Western metaphysics one of its greatest books, Process and Reality (1929).

Whitehead had an unwavering faith in the possibility of understanding existence and a superb power to construct a scheme of general ideas broad enough to overcome the classic dualisms. But he knew that no system can do more than make an approach, somewhat more adequate than its predecessors, to understanding the infinitude of existence. He had seen the collapse of the long-entrenched Newtonian system of physics, and he never forgot its lesson. Henceforth dogmatic assurance, whether in philosophy, science, or theology, was his enemy.

Adventures of Ideas (1933) was Whitehead's last big philosophical book and the most rewarding one for the general reader. It offered penetrating, balanced reflections on the parts played by brute forces and by general ideas about humanity, God, and the universe in shaping the course of Western civilization. Whitehead emphasized the impulse of life toward newness and the absolute need for societies stable enough to nourish adventure that is fruitful rather than anarchic. In this book he also summarized his metaphysics and used it to elucidate the nature of beauty, truth, art, adventure, and peace. By “peace” he meant a religious attitude that is “primarily a trust in the efficacy of beauty.”

Except for an insufficient familiarity with Karl Marx and Sigmund Freud, Whitehead was at home in both the scientific and the literary cultures of his time. Young people flocked to “Sunday evenings,” which his wife skillfully managed. Here the spare, rosy-cheeked man, who might have been of average height if he had not been so stooped, talked to them in a high-pitched but gentle voice—talked not about his system but about whatever was on their minds, sharply illuminating it from a broad and historical perspective.

In his Harvard lectures, as in his books, Whitehead liked best to explore the scope of application of an idea and to show how intuitions that were traditionally opposed could supplement each other, which he did by dint of his own ideas. Most students found attendance at his lectures a great experience. Harvard did not retire him until 1937.

In his first years in the United States, Whitehead visited many eastern and midwestern campuses as a lecturer. Though he loved Americans, he remained always very much an Englishman. A Fellow of the Royal Society since 1903, he was elected to the British Academy in 1931. In 1945 he received the Order of Merit. After his death his body was cremated, and there was no funeral. His unpublished manuscripts and correspondence were destroyed by his widow, as he had wanted.

Whitehead has not had disciples, though his admirers have included leaders in every field of thought. His educational and philosophical books have been translated into many languages. His metaphysics has been keenly studied, in the United States most of all. What is now called Whitehead's “process theology” is easily the most influential part of his system; this is partly due to the influence of the U.S. philosopher Charles Hartshorne.

Whitehead's habit of helpfulness made him universally beloved. Though his courtesy was perfect, there was nothing soft about him; never contentious, he was astute, charitable, and quietly stubborn. He had a realistic, well-poised mind and a fine irony free of malice. Whitehead combined singular gifts of intuition, intellectual power, and goodness with firmness and wisdom.