Much of Immanuel Kant’s work is a response to the philosophical debate between rationalism and empiricism, which characterized much of Enlightenment philosophy in the late 17th and 18th centuries. The rationalist view, which was arguably first articulated by the ancient Greek philosopher Plato, is that people are born already having certain concepts and ideas. Further, Plato would argue that what people know through abstract and logical reasoning and intuition is superior to any knowledge gained through experience of the bodily senses alone. In the modern era, it was the view reasserted by the French philosopher René Descartes (1596-1650)—famous for his dictum, “I think therefore I am”—and further developed by the Jewish-Dutch philosopher Baruch Spinoza (1632-1677) and the German mathematician and philosopher Gottfried Liebniz (1646-1716).

While Descartes’s rationalism became popular among scholars and philosophers in continental Europe, the rival empirical school of thought was developing in Britain. Early proponents of empiricism included Francis Bacon (1561-1626), John Locke (1632-1704), and David Hume (1711-1776). Empiricists argued that knowledge is only truly gained through observation and direct experience. Hume argued for a particularly radical understanding of empiricism. He suggested that relationships of cause and effect can never truly be known, since causation cannot be experienced directly through the senses (for example, we cannot know for sure that a beach ball will always float in the water through our senses alone, we can only assume it will happen through “custom,” meaning that we know it has happened numerous times before).