As a mathematical logician who wrote and published prolifically, Mr. Quine was often perceived as a philosopher who focused his analytic talents on many apparently disparate doctrines and theses. Yet those who understood him best insisted on his status as a system builder, or a thinker who addressed and attempted to answer the larger questions of philosophy.
Stuart Hampshire, a fellow philosopher, called him in 1971 ''our most distinguished living systematic philosopher.''
Like most philosophers, Mr. Quine set out to define the reality of the world and how humans fit into that reality. He concluded that a person can only understand the world empirically, or through direct experience of it. In ''The Philosophy of W. V. Quine: An Expository Essay,'' a study that the subject endorsed, Roger F. Gibson Jr. wrote that if Mr. Quine's project could be summed up in a single sentence, that sentence would read, ''Quine's philosophy is a systematic attempt to answer, from a uniquely empiricistic point of view, what he takes to be the central question of epistemology, namely, 'How do we acquire our theory of the world?' ''
Mr. Quine's answer, in a nutshell, began by rephrasing the question to read, ''How do we acquire our talk about the world?'' In his radically empiricist view, nothing that humans know about the world lies outside the realm of language, and so he insisted that any theory of knowledge depended on a theory of language, which he duly set about developing and which became the framework of his philosophy.
In pursuing this objective Mr. Quine found himself in a distinct position among his contemporaries. Among 20th-century philosophers were the so-called historicists -- those willing to speculate about and proclaim metaphysical truths independent of empirical evidence -- and the formalists -- those mathematical logicians who considered philosophy an autonomous, ahistorical discipline that replaced metaphysical speculation with scientific thinking. In the battle between followers of those views, Mr. Quine was a standard-bearer in the latter camp, a hero of empiricism who once declared that ''philosophy of science is philosophy enough.''
This led him to fight in the ranks of the so-called logical positivists, or those like his European friends A. J. Ayer and Rudolf Carnap, who asserted that all statements of truth must be based on observable data. He even helped to shift the main ground of their battle from Europe to the United States. Yet Mr. Quine later challenged them in what is arguably the best known of his many published essays, ''Two Dogmas of Empiricism.'' It first appeared in the Philosophical Review in January 1951 and was reprinted in 1953 in a collection of his essays titled ''From a Logical Point of View.''
The essay set out to undermine the two main points of positivism. First, Mr. Quine rejected the fundamental distinction between what Kant had called analytic and synthetic propositions, or the distinction between statements that seem true no matter what (like ''all bachelors are unmarried'') and those that are true because of the way things happen to be (like ''Mr. X is a bachelor''). (This position, incidentally, earned him a place in Dan Dennett's ''Philosophers' Lexicon,'' in which names of philosophers are construed as verbs or common nouns: to ''quine'' is to repudiate a clear distinction.)
To deny the distinction between analytic and synthetic statements meant that nothing could be known independent of experience.
Second, the essay argued against what he called the dogma of reductionism, or ''the belief,'' as he put it, ''that each meaningful statement is equivalent to some logical construct upon terms which refer to immediate experience.'' In other words, nothing in a person's experience lies beyond meaningful statement about it.
Although this seemed to amount to a rejection of all knowledge of a reality beyond our senses, Mr. Quine did not completely shut the door to a world out there. The alternative that he preferred was this explanation: ''The totality of our so-called knowledge or beliefs, from the most casual matters of geography and history to the profoundest laws of atomic physics or even of pure mathematics and logic, is a man-made fabric which impinges on experience only along the edges.''
This position led him to two more conclusions about the nature of meaning and what humans can know about objective reality. One, enunciated in his 1960 book, ''Word and Object,'' was that when translating from one language to another, or even from one sentence to another within the same language, there were bound to be many contradictory ways to understand the meaning and that there was no sense in asking which of them was right.
This works, in his view, with what he called ontological relativity, which holds that because our theories of what exists are not sufficiently determined by the experiences that give rise to them, quite different accounts of what there is, each with its own interpretation of the evidence, may be equally in accord with that evidence. To the objection that surely at least physical objects must figure in all theories of what is out there, Mr. Quine responded, yes, in practice, although he said he considered physical objects a matter of convenience.
''As an empiricist,'' he wrote toward the end of ''Two Dogmas of Empiricism,'' ''I continue to think of the conceptual scheme of science as a tool, ultimately, for predicting future experience in the light of past experience. Physical objects are conceptually imported into the situation as convenient intermediaries not by definition in terms of experience, but simply as irreducible posits comparable, epistemologically, to the gods of Homer.''
He concluded: ''For my part I do, qua lay physicist, believe in physical objects and not in Homer's gods; and I consider it a scientific error to believe otherwise. But in point of epistemological footing, the physical objects and the gods differ only in degree and not in kind. Both sorts of entities enter our conceptions only as cultural posits.''
Willard Van Orman Quine, or Van to his friends, was born on June 25, 1908, in Akron, Ohio, the second son of Cloyd Robert Quine, a machinist and successful businessman, and Harriet (Van Orman) Quine. The surname is from the Celtic language Manx, Mr. Quine's paternal grandfather having emigrated from the Isle of Man to Akron. Mr. Quine was named Willard after his mother's brother, a mathematician.
The nominal connection seemed to work. He took a liking to mathematics in high school and majored in it at Oberlin, although philology and philosophy also interested him early. (During his junior year at college his mother presented him with Whitehead and Russell's ''Principia Mathematica'' and Skeat's Etymological Dictionary, the latter of which, he said, ''I persistently consulted and explored over the succeeding half century,'' a fact attested to by the liveliness and clarity of his writing.)
About his subsequent teaching career he said: ''What I enjoyed most was more the mathematical end than the philosophical, because of it being less a matter of opinion. Clarifying, not defending. Resting on proof.'' His honors thesis at Oberlin used the system of ''Principia Mathematica'' to prove with 18 pages of symbols a law having to do with ways of combining logical classes. (He later edited the 18 pages down to three for the Journal of the London Mathematical Society.) His thesis landed him at Harvard University, where he switched to philosophy to study with Alfred North Whitehead. (''He radiated greatness and seemed old as the hills,'' Mr. Quine wrote in his autobiography, ''The Time of My Life.'' ''I retained a vivid sense of being in the presence of the great.'')
Only two years later, in 1932, he had earned his Ph.D., his dissertation being an attempt, in his words, ''like 'Principia,' to comprehend the foundations of logic and mathematics and hence of the abstract nature of all science.'' (It was published in revised form by the Harvard University Press with the title ''A System of Logistic.'')
He then went to Europe on a Sheldon Traveling Fellowship and spent the next year in Vienna, Prague and Warsaw, where he studied, lectured and met various members of the Vienna Circle of logical positivists, among them Philipp Frank, Moritz Schlick, Alfred Tarski, A. J. Ayer, their English spokesman, Kurt Godel (who preferred not to be called a logical positivist), and Rudolf Carnap, from whom, Mr. Quine said, ''I gained more . . . than from any other philosopher.'' (In Vienna he dropped a note to Wittgenstein, who never responded.)
The European interlude allowed him to indulge his lifelong passion for crossing borders (perhaps related to his penchant for denying distinctions, or, more likely, inspired by a youthful ardor for philately), which, according to a count he made late in his life, was to take him into 118 countries, over another 19, and within sight of 8 more, among the last being China, Oman and Bangladesh. His autobiography describes many of these visits somewhat matter-of-factly. His early love of geography was also reflected in a gift for drawing maps, which later extended to sketching portraits, several of which appear in his autobiography.
In 1933 he returned to Harvard as a junior fellow in the newly formed Society of Fellows, which meant three years of unfettered research. Another junior fellow that year was the psychologist B. F. Skinner, with whom Mr. Quine came to share, as he put it, ''the fundamental position that an explanation -- not the deepest one, but one of a shallower kind -- is possible at the purest behavioral level.''
In 1936 Mr. Quine became an instructor in philosophy at Harvard, where he taught, off and on, for the rest of his life, interrupted only by service in the Navy during World War II, when he did cryptanalytic work translating the German submarine cypher in Washington, as well as by his globe-girdling travels, the bestowal of medals, prizes and some dozen-and-a-half honorary degrees, and by lectures and classes delivered all over the world.
His students at Harvard included Donald Davidson and Burton Dreben, the philosophers; Tom Lehrer, the mathematician and songwriter; and Theodore J. Kaczynski, the Unabomber (''although I don't remember him,'' Mr. Quine told an interviewer, ''he tied for top, 98.9 percent'').
In the Navy he met Marjorie Boynton, a Wave in his office who became his second wife in 1948. His first marriage to Naomi Clayton in 1930 ended in divorce in 1947. His second wife died in 1998. He is survived by two daughters from his first marriage, Elizabeth Quine Roberts and Norma Quine; a son and daughter from his second, Douglas Boynton Quine and Margaret Quine McGovern; five grandchildren; and a great-grandson.
Mr. Quine published about 20 books, some reprinted in multiple editions and several translated into as many as eight languages. One of the more accessible works, ''Quiddities: An Intermittently Philosophical Dictionary'' (1987), was praised in The New York Times by John Gross in general for ''a deadpan humor that can light up even the most austere subjects'' and in particular for commending the state lottery as '' 'a public subsidy of intelligence,' on the grounds that 'it yields public income that is calculated to lighten the tax burden of us prudent abstainers at the expense of the benighted masses of wishful thinkers.' ''
At the end of ''The Time of My Life,'' Mr. Quine wrote: ''I am orderly and I am frugal. For the most part my only emotion is impatience,'' he continued. ''I am deeply moved by occasional passages of poetry, and so, characteristically, I read little of it.''
Although a ''Quine'' is defined in the New Hackers Dictionary as ''a program that generates a copy of its own source text as its complete output,'' Mr. Quine never wrote on a computer, always preferring the 1927 Remington typewriter that he first used for his doctoral thesis. Because that project contained so many special symbols, he had to have the machine adjusted by removing the second period, the second comma and the question mark.
''You don't miss the question mark?'' a reporter once asked him.
''Well, you see,'' he replied, ''I deal in certainties.''
By CHRISTOPHER LEHMANN-HAUPT, December 29, 2000 © The New York Times Company