Chisholm defended the possibility of empirical knowledge by appeal to a 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.
