The Problems of Philosophy

Imagine an apple sitting on top of a table. Most people can recognize the fruit with ease, even if it varies in color, size, or shape. These people may also have specific questions about the fruit: How did the apple get there? Can I eat it? Philosophers such as Bertrand Russell, on the other hand, ask a different type of question. Epistemologists are concerned with human understanding: How do I know this is an apple? Where does that knowledge come from? Questions like these have preoccupied philosophers since the fifth century when Plato first asserted that knowledge is innate. His student Aristotle challenged this idea by suggesting that knowledge is gained through observation and experience. These Ancient Greek philosophers established the foundation for a field of study called epistemology, which explores the nature and limitations of knowledge. Epistemology uniquely turns the philosopher’s focus inward; epistemologists spend their time thinking about thinking. Rather than wondering about the tastiness of the apple, epistemologists are concerned with how people perceive, recognize, and think about the existence of the fruit.

Philosophical arguments about epistemology often center around the concepts of priori and posteriori. Priori knowledge represents innate knowledge, independent of sensory experience. This type of knowledge represents universal truths. Plato believed that the external world contains forms and essences that humans recognize and make sense of independent of observation or experience. For strict followers of priori knowledge, a human’s ability to recognize something like an apple comes from an innate understanding of what an apple is. Just as Plato believed that humans hold an innate understanding of forms, philosophers such as René Descartes and Immanuel Kant enveloped innate knowledge into their works. Descartes—famous for the phrase Cogito, ergo sum, which means “I think, therefore I am”—believed that both types of knowledge exist and argued that some forms of knowledge, such as the existence of the self, are undeniably innate. Kant suggested that priori concepts like space and time help shape experiences and impact posteriori knowledge.

Posteriori knowledge is gained through observation and sensory experience. In An Essay Concerning Human Understanding (1689), John Locke proposed his theory of empiricism, which argues that all people are born without knowledge. Their minds are a blank slate, referred to as the tabula rasa. Locke believed that humans gain knowledge through sensory experience. The blank slate eventually becomes filled with knowledge by interacting with and observing the physical world. A person’s understanding of an apple is shaped by previous encounters with apples.

However, Locke was not the only philosopher of the 17th and 18th centuries seeking to unlock epistemology. George Berkeley presented an opposing theory called idealism, which asserts that the physical world does not exist outside of the mind and its ideas. Figures such as Berkeley and G. W. F. Hegel proposed that reality exists only within the minds of individuals. These philosophers argued that knowledge about the physical world is a mental construct. Within the field of idealism, the apple does not exist, and one’s understanding of the apple is indicative of the singular reality of the mind.

Russell was influenced by Locke’s work and the theory of empiricism. However, he saw knowledge as something more nuanced and suggested that the empiricist tradition had several limitations, including the potential for humans to shape knowledge with their own biases, skepticism, and untrustworthy senses. Russell’s work on epistemology by using logical analysis was partly a reaction to idealism. Russell challenged this ideology by suggesting that knowledge can be understood logically and that truth is mind independent. His theory of direct realism challenges idealism. In this theory, a person’s understanding of the apple is a direct result of a person interacting with the physical world. A person sees a real external object and connects with it through perception and experience. Like many of the philosophers who preceded him, Russell blended priori knowledge, which he believed exists inside mathematical and logical truths, and posteriori knowledge, gained through empirical observation and sensory experience.