The philosopher Peter Geach has died. He taught for many years at the Universities of Birmingham and Leeds, and also as a Visiting Professor at the University of Warsaw. He wrote many influential books and articles, several of which are noted here by the philosopher John Haldane. In 1941 Geach married Elizabeth Anscombe, and together they had seven children. (Here is a famous photograph of Geach and Anscombe, taken in 1990.) Along with Anscombe and Michael Dummett (whose death I noted in 2011), Geach was one of the very most important Catholic philosophers of the twentieth century.

Geach was born in London in 1916. He was raised mostly by his father, who had been trained in philosophy but had never been able to secure a prestigious teaching position, and saw in his son a worthy pupil. On Geach's telling, his father had the habit of changing his religious beliefs several times a year—always quite suddenly, and always with strong arguments for the change. As a young man Geach would follow his father through these transitions, and he recalls being teased by a school friend on returning from college: "Hullo, Geach! Good hols? Does God exist this term?"

Under his father's tutelage, one of Geach's earliest philosophical influences was the metaphysician J.M.E. McTaggart, who infamously argues in his 1908 book The Unreality of Time for, well, the unreality of time. Geach's initial resistance to McTaggart's views gave way to what he calls "the irresistible force of reasoning," and he became for some time a firm adherent to McTaggart's system, his views "honed to a sharp edge by controversy." After enrolling as a student at Oxford, Geach's intellectual combatants came to include increasing numbers of Catholics. He tells the rest:

I was certainly cleverer than they, but they had the immeasurable advantage that they were right—an advantage that they did not throw away by resorting to the bad philosophy and apologetics then sometimes taught in Catholic schools. One day my defences quite suddenly collapsed: I knew that if I were to remain an honest man I must seek instruction in the Catholic Religion. I was received into the Catholic Church on May 31, 1938.

I suspect that only someone who had seen his father undergo dozens of conversions could have changed his own views so suddenly. This time, however, it took.

As the above excerpts reveal (they are all from Geach's "Philosophical Autobiography," published in Peter Geach: Philosophical Encounters, ed. Harry A. Lewis), in addition to being an extraordinary philosopher Geach was an exquisitely talented writer. He could also be very funny, even in addressing technical philosophical topics: for example, there is a crucial passage in his well-known book Mental Acts where it will gradually dawn on the careful reader that Geach has adopted the prose style of Thomas Aquinas and is mirroring several Thomistic distinctions; he reveals in the following paragraph that this is no accident, as the passage follows almost phrase-for-phrase an article from the Summa Theologiae. The depth and scope of Geach's learning is evident in every page of his writing, where he draws freely on his knowledge of philosophical history in discussing complex issues in metaphysics and the philosophy of mind and language.

Along with Aquinas and McTaggart (whose system he presents in his 1982 book Truth, Love, and Immortality), Geach's main philosophical heroes were Aristotle, Ludwig Wittgenstein, and Gottlob Frege. (Remarkably to me, in his autobiography Geach also has a lot of positive things to say about Thomas Hobbes.) Like any good Thomist, and unlike many poor ones, Geach did not work backwards from predetermined conclusions, but always let the reasons lead him, confident that truth would prevail. Here his how Geach describes his philosophical process in his autobiography, contrasting it with the "more adventurous" strategy of his wife Anscombe:

My mind works differently; the shocking theses I have defended in the philosophy of logic were reached not in bold leaps but by slow steps, with each step mentally tested against a multitude of examples and objections before the next step was taken. Both of us, I hope, have avoided two vices: frivolous change of mind, and adherence to past sayings in the desire to have been right rather than be right.

This difference in philosophical style also made Geach a very different sort of writer than Anscombe; whereas her writings lack the kind of evident structure that today's philosophers mostly take for granted, Geach is more obviously orderly in his presentation. But they shared a conviction that good philosophy requires close attention to the workings of language—an insight that in his autobiography Geach credits to Aquinas:

While studying Aquinas...I could not help noticing that he is linguistically very self-conscious, in a way that McTaggart is not: again and again there is a careful discussion of logico-grammatical points, like the roles of nouns, adjectives, verbs, and particles; he uses the best contemporary work of logicians (sophistae), but when their work will not serve his ends he devises tools of his own to analyse the language of his theological arguments.

Like Aquinas, Geach did not think the tools of logical analysis were applicable only to "abstract" topics like the nature of time or the semantics of singular terms. He also wrote, in the very same style, about love, hope, the soul, the efficacy of prayer, and whether we survive our deaths. He was an immensely important thinker, and his writings will remain influential for many years to come. May he rest in peace.