Sir Michael Dummett, who has died aged 86, was one of the greatest British philosophers of the 20th century. He was also an international authority on tarot cards, a campaigner for racial justice and a devoted family man. His wife, Ann, was a co-worker in his fight against racism and collaborated with him on a number of publications on the subject.
Dummett was a staunch advocate of “analytic” philosophy, the fundamental tenet of which he took to be that “the philosophy of language is the foundation of all other philosophy”. He also once characterised it as “post-Fregean philosophy”, the 19th-century German philosopher Gottlob Frege having done as much as anyone to treat the philosophy of language in this way. Much of Dummett's own work was accordingly devoted to the interpretation and exposition of Frege's ideas, and he will be as well remembered for his exegesis of Frege as he will for his own seminal contributions to analytic philosophy.
Frege held that the way in which the words in a sentence combine reflects the structure of the thought that the sentence expresses. In the sentence “Michael smokes,” a proper name combines with a verb so as to express the thought that a particular person, Michael, indulges in a particular activity, smoking. This thought is true if Michael does in fact smoke, and false otherwise.
On this apparently innocuous and simple basis, Frege erected an elaborate set of ideas that have had an immense influence. Nevertheless, Dummett believed that Frege made certain assumptions concerning truth and falsehood that could be called into question. Frege allowed for the possibility of a thought that was neither true nor false. An example would be the thought that Father Christmas smokes. Given that there is no such person as Father Christmas, then neither is there anything to make this thought true or false. But Frege was not in the least reluctant to admit that a thought could be true or false without our having any way of telling which. An example might be the thought that Plato would have enjoyed smoking. This is what caused Dummett to pause.