Chisholm's first major work was Perceiving. His epistemological views were summed up in a popular text, Theory of Knowledge, which appeared in three very different editions. His masterwork was Person and Object, its title deliberately contrasting with W. V. O. Quine's Word and Object. Chisholm was a metaphysical Platonist in the tradition of Bertrand Russell, and a rationalist in the tradition of Russell, G. E. Moore, and Franz Brentano; he objected to Quine's anti-realism, behaviorism, and relativism. Chisholm defended the possibility of empirical knowledge by appeal toa priori epistemic principles whose consequences include that it is more reasonable to trust your senses and memory in most situations than to doubt them. His theory of knowledge was also famously "foundationalist" in character: all justified beliefs are either "directly evident" or supported by chains of justified beliefs that ultimately lead to beliefs that are directly evident. He also defended a controversial theory of volition called "agent causation" much like that of Thomas Reid. He argued that free will is incompatible with determinism, and believed that we do act freely; this combination of views is known as libertarianism. He developed a highly original theory of first person thought according to which the things we believe are properties, and believing them is a matter of self-attributing them. Chisholm was also famous for defending the possibility of robust self-knowledge, and an objective ethics of requirements similar to that of W. D. Ross. Chisholm's other books include The Problem of the Criterion, Perceiving, The First Person and A Realist Theory of the Categories, though his numerous journal articles are probably better known than any of these. Chisholm read widely in the history of philosophy, and frequently referred to the work of Ancient, Medieval, Modern, and even Continental philosophers. Nonetheless, he greatly respected the history of philosophy, in the face of a prevailing indifference among analytic philosophers. Chisholm translated some work by Brentano and by Husserl, and contributed to the post-1970 renaissance of mereology.
Chisholm argued for the primacy of the mental over linguisticintentionality, as suggested in the title of Person and Object that was deliberately contrasted with Quine's Word and Object. In this regard, he defended the direct attribution theory of reference in The First Person. He argues that we refer to things other than ourselves by indirectly attributing properties to them, and that we indirectly or relatively attribute properties to them by directly attributing properties to ourselves. Suppose the following bed scene: If I were M and "U" were W, then I could directly attribute to myself the property or M-B-W, while indirectly to "U" the property or W-B-M, thereby referring to "U". That is, to say is relatively to say, or to explicate M-B-W is to implicate W-B-M. His idea of indirect attribution is relevant to John Searle's "indirect speech act" and Paul Grice's "implicature", in addition to entailment.
"Chisholming"
Stylistically, Chisholm was known for formulating definitions and subsequently revising them in the light of counterexamples. This led to a joke definition of a new verb: While intended as a joke, the term has found some use in serious philosophical papers.
