Timothy Williamson's education began at Leighton Park School and continued at Henley Grammar School. He then went to Oxford University. He graduated in 1976 with a B.A. (first class honours) in Mathematics and Philosophy, and in 1981 with a doctorate in philosophy (DPhil) for a thesis examining "The Concept of Approximation to the Truth".
He is currently the Wykeham Professor of Logic at the University of Oxford, and Fellow of New College, Oxford. He was previously Professor of Logic and Metaphysics at the University of Edinburgh (1995–2000). Fellow and Lecturer in Philosophy at University College, Oxford (1988–1994).
And Lecturer in Philosophy at Trinity College, Dublin (1980–1988). He was president of the Aristotelian Society from 2004 to 2005. He is a Fellow of the British Academy (FBA), the Norwegian Academy of Science and Letters, Fellow of the Royal Society of Edinburgh (FRSE) and a Foreign Honorary Fellow of the American Academy of Arts & Sciences.
On vagueness, he holds a position known as epistemicism, which states that every seemingly vague predicate (like "bald", or "thin") actually has a sharp cutoff, which is impossible for us to know. That is, there is some number of hairs such that anyone with that number is bald, and anyone with even one more hair is not. In actuality, this condition will be spelled out only partly in terms of numbers of hairs, but whatever measures are relevant will have some precise cutoff.
This solution to the difficult sorites paradox was considered an astonishing and unacceptable consequence, but has become a relatively mainstream view since his defense of it. Williamson is fond of using the statement, "no one knows whether I am thin" to illustrate his view. In epistemology, he suggests that the concept of knowledge is unanalyzable.
This goes against the common trend in philosophical literature up to that point, which was to argue that knowledge could be analysed into constituent concepts. (Typically this would be justified true belief plus an extra factor) He agrees that knowledge entails justification, truth and belief, but that it is conceptually primitive. He accounts for the importance of belief by discussing its connections with knowledge, but avoids the disjunctivist position of saying that belief can be analyzed as the disjunction of knowledge with some distinct, non-factive mental state.
Fellow: Royal Society Edinburgh, British Academy. Member: American Academy Arts & Sciences (foreign honorary), Norwegian Academy of Sciences and Letters (foreign member).
Married; 3 children.