Logic and Philosophy of Language:
* Mental Acts: (1957) - A classic work on the philosophy of mind, particularly focusing on the nature of mental acts like believing and wanting.
* Logic Matters: (1980) - A collection of Geach's essays on logic, including discussions on modal logic, free logic, and the logic of predicates.
* Reference and Generality: (1962) - A critical examination of the relationship between language and the world, addressing issues of reference, predication, and quantifiers.
Ethics and Moral Philosophy:
* The Virtues: (1977) - An influential work on virtue ethics, challenging traditional conceptions of moral reasoning and arguing for the importance of character.
* God and the Soul: (1969) - Explores philosophical questions about the existence of God, the nature of the soul, and the relationship between them.
Other Works:
* The Third Man Argument: (1962) - An essay examining the classic philosophical puzzle regarding the nature of universals and the possibility of a "third man" existing beyond the instances of a given concept.
* The Philosophical Works of Gottlob Frege: (1972) - A translation and commentary on the work of the important German logician and philosopher Gottlob Frege.
Geach's work is characterized by its clarity, rigor, and originality. He was known for his precise and incisive arguments, his willingness to challenge conventional wisdom, and his deep understanding of the history of philosophy.
These are just some of the most notable works by Harold Geach. You can find more information about his writings and publications by searching for him in academic databases like JSTOR or PhilPapers.