MOVING TO FRONT FROM DEC. 22--UPDATED
Professor Geach was well-known for many books and articles on topics in philosophy of language and mind (including what is now known as the Frege-Geach probject for ethical non-cognitivism), as well as for work in the genre now known as "analytical Thomism." He spent most of his teaching career at the University of Birmingham and then the University of Leeds, where he was emeritus. Here is Steve Pyke's famous photo of Geach and his wife G.E.M. Anscombe. I will add links to memorial notices as they appear.
UPDATE: Philosopher John Haldane (St. Andrews) has written an informative memorial of Professor Geach, which he kindly invited me to share with readers:
The death of Peter Geach on 21st December 2013 at the age of 97 marks the passing of one of Anglophone philosophy's most distinctive and gifted figures. Geach published widely over seven decades in the areas of logic, language, mind, religion and ethics. His first article "Designation and Truth" appeared in Analysis in 1948, and his last was published in the same journal in 2006. Entitled "The Labels" it begins "Once upon a time in China there was a wicked king. His hobby was logic" and it concerns the King's intellectual battles with and eventual defeat of a "very clever logician Lo-sou". Numbering fewer than 300 words, it is an illustrated example of a problem posed by his late wife Elizabeth Anscombe when she herself was 81. "Lo-sou" was the Chinese name for Bertrand Russell. In the previous issue of Analysis Geach published "The Tractatus is not all rubbish", a 200 word response to a critic of Wittgenstein's propositional logic.
Among analytical philosophers Peter Geach was without peer as a literary stylist. One may disagree with his judgements and take exception to the terms in which they were sometimes expressed; yet his writing is a model of clear and precise English, devoid of pseudo-subtlety but animated by a learned literary spirit. Like Johnson and Chesterton, (both of whom he admired) Geach is a pleasure to read; unlike them he commanded both plain prose and the technical languages of Greek and medieval philosophy, as well being a master of logic and a powerful dialectician.
He made light of any claim to be a creative logician; yet his contributions to the philosophy of logic are rightly admired, and his deployment of logical insights in the course of non-technical argumentation combines lightness with efficacy. Four examples of the latter deserve mention on account of their insight and influence:
1. In "Frege's Grundlagen" (Philosophical Review 1960) Geach observed that the development of arithmetic can proceed validly within the Fregean system from Hume's principle without reliance on the extension operator. The same point was later developed by Charles Parsons and Crispin Wright.
2. In "Good and Evil" (Analysis, 1956) Geach notes that in its most common and natural uses "good" is an attributive adjective, the criteria for its application being provided by the substantive which is qualifies - as in 'good knife'. This was subsequently deployed by Philippa Foot and many others.
3. In "Ascriptivism" (Philosophical Review, 1960) Geach pointed out that for inferences to be valid, expressions occurring in both asserted and unasserted uses have to have the same meaning, and that this poses problems for attitudinal accounts of 'voluntary', 'intentional' and 'good' and 'bad'. It is worth noting that while the 'Frege-Geach' problem is more or less universally introduced n discussions of meta-ethical expressivism, Geach's first presentation of it was mainly concerned with philosophy of action.
4. In "On Worshipping the Right God" (c. 1960, published in God and the Soul, 1969) Geach distinguishes between 'personal' and 'impersonal' uses of 'to refer' and gives examples where a speaker refers though the definite description he uses is false, and others where the description is satisfied by someone other than the person to whom the speaker uniquely refers. Later in 1960s and in the decade following, such distinctions and examples became standard in the formulation of 'direct reference' theories - though unlike many who turned in that direction he also argued that the use of proper names logically implies the existence of associated kind concepts.
Geach also made important early contributions to logic in the areas of plural quantification, the sortal-dependency of identity, entailment, and intentional identity. Some of his ideas have resulted in the entry of expressions into the philosophical lexicon including 'Cambridge Change', 'predicable', 'pronoun of laziness', 'relative identity', Shakespearean context'. To the extent that Geach drew inspiration from other philosophers it tended to be from figures of the past, though he had a high regard for Kripke, Prior, and Quine which in each case was fully reciprocated.
ANOTHER: An obituary from The Guardian.
AND ANOTHER: Philosopher John Schwenkler (Forida State) on Geach at Commonweal.
AND ANOTHER: The Telegraph. (Thanks to David Gordon for the pointer.)