David Hume (1711–1776) was born in Berwickshire, near Edinburgh, in Scotland. Hume was a philosopher, historian, economist, and essayist. He attended the University of Edinburgh from the age of 11 but left at 15 to pursue private study. His skepticism concerning religion kept him from getting the Chair of Ethics and Pnuematical Philosophy at the University of Edinburgh. When he failed to get the position, he accompanied his cousin as a secretary on a military mission against the French in Canada. After his trip to Canada, Hume travelled with his cousin to Vienna and Turin. He wrote at least one important philosophical treatise during this trip. When he returned to Scotland he accepted a position as a librarian and completed the six-volume History of England, which became a best seller. Hume lived in Paris as secretary to the British ambassador to France for three years. A fleeing Jean-Jacques Rousseau accompanied Hume on his return trip to England. Hume lived in London for a year, serving as under-secretary of state. Returning to Edinburgh, he built a house where he remained for the rest of his life.
Hume’s empiricist philosophy centered on his assertion that the science of man is the basis for all other sciences. In other words, one must understand how the human mind works in order to properly understand other sciences. Hume believed that there was no constant, permanent self. Rather, the self is always the sum of one’s sensations and reflections. Knowledge, likewise, is derived from sensations and reflections on those sensations. Consequently, propositions about objects are semantically equivalent to propositions about one’s experiences. While we can have belief in something that is not directly observable, we cannot have knowledge about that thing. Hume taught that “cause” and “effect” were qualities of human perception, not necessarily of the object itself. For example, we see ball A strike ball B; following that, ball B moves. Hume argued that while we perceive ball A to have caused the effect of ball B moving, those qualities might not exist in the balls themselves. The habit of seeing a ball strike another ball, followed by the movement of the second ball, leads us to perceive that ball A caused ball B to move. Hume wasn’t saying that ball A didn’t cause ball B to move; just that we cannot empirically observe the mechanism for the movement, and thus we cannot have knowledge of it.