Ideas and sensations
Gifford observes that Mulligan's "I remember only ideas and sensations" resembles “the essentially mechanistic concept of the human psyche developed by the English philosopher David Hartley (1705-57),” under the influence of John Locke.
A number of eighteenth century philosophers drew from Locke's empiricist epistemology the conclusion that reliable understanding of the external world is impossible; one has only one’s remembered traces of past experiences, and the experiences were themselves only sensations formed in one’s subjective consciousness. Among the entities effaced by such subjective skepticism are, inevitably, other subjects, and Mulligan is happy to use this effacement as an excuse for self-centered hedonism. He conveniently omits to mention any moral sensations that might have formed in his consciousness as a result of speaking so callously about his friend.