A Treatise Concerning the Principles of Human Knowledge

Irish philosopher and Anglican Bishop George Berkeley (1685-1753) wrote A Treatise Concerning the Principles of Human Knowledge in 1710. The short work expounds Berkeley’s philosophy of immaterialism, a form of empiricism asserting that nothing exists outside of a mind’s perception of it. Objects, therefore, are not things, but ideas. Berkeley’s philosophy critiques that of contemporary empiricists John Locke and David Hume, who contended that the mind can perceive the material world in abstract and that matter exists independent of a perceiving mind.

In Berkeley’s philosophy, a thing in the material world can never be understood in abstract terms because humans can only refer to their prior knowledge of the thing that they are perceiving. Empiricists believe that all knowledge comes through sensory experiences, and Berkeley takes this idea a step further to assert that when we perceive something, we are actually perceiving our own ideas about that thing. In his Treatise, Berkeley replaces the word “thing” with “idea” to be clear about the nature of its being. He asserts that first, human minds sense something—an object’s pleasant or unpleasant odor, its soft or prickly surface, its large or small size, and square or round shape. The mind organizes these ideas in a familiar way and perceives something it recognizes. Since these ideas exist only when they are perceived, Berkeley argues, if the mind did not exist to perceive them, the objects—or ideas—would not exist either.

To say that something exists means that it is perceived by some mind, whether it is the mind of a human being or of God. Reality does not exist outside of or separate from the mind; rather, everything the mind perceives is a result of its own mental reflection.

Berkeley’s goal in the Treatise is to argue against skepticism (philosophy of doubt) and atheism (the denial of the existence of God) to foster an awareness of God’s presence and inspire greater piety toward Him. Berkeley believes that there is order in the universe: A creator spirit, God, is responsible for our world and our ability to perceive things.

Written when Berkeley was only 25 years old, the book prompted widespread discourse upon its publication. It is now considered one of the major works of his career.

The Treatise is divided into 156 numbered paragraphs, which I refer to as sections. To avoid repetition, I combine the summary and analysis of these sections. This guide refers to the 1957 edition of the Treatise published by The Library of Liberal Arts.

Summary

Berkeley begins the Introduction by reflecting on the difficulty of attaining truth. This difficulty is deceptive: Our desire and longing for truth prove that it is within reach for us. The “doubtfulness and uncertainty” (6) in philosophy are due to the “wrong use” of reason and language, not to any inherent obscurity in things. It is this unnecessary, manmade obscurity that Berkeley intends to dispel in the Treatise.

First, Berkeley analyzes the way the mind perceives things around it. When the mind perceives an object, it perceives its various qualities and attributes. Although in reality these qualities all exist together, the mind is able to abstract the various qualities and consider them separately. Berkeley argues that the mind cannot conceive of concepts like “color” or “man” in the abstract. Instead, when it thinks of “color” it thinks of a particular color, and when it thinks of “man” it thinks of a man with particular attributes. Berkeley concludes that abstract thought, while a useful tool of philosophy, does not reflect the way things really are. By the end of the lengthy Introduction, Berkeley has established two major themes of his book: the dangers of abstract thought and the misuse of language, both of which create pitfalls in philosophy.

As the book proper (“Part 1”) begins, Berkeley discusses how we perceive the things around us using our senses, mind, memory, and imagination. Our senses help us form ideas about the world around us. There are two aspects of this process. There is the thing being perceived, and there is the being who is perceiving. The first Berkeley calls an “idea” and the second he calls “mind,” “spirit,” or “soul.” By its very nature, an idea cannot exist without the mind perceiving it. In Section 3, Berkeley states his maxim that “esse is percipi”: to exist is to be perceived.

Spirits are active and personal, whereas ideas are passive and have neither power in themselves nor personality. Therefore, it must be a spirit that gives us our ideas of the things we perceive, and that spirit is God. As a consequence of this, Berkeley in Section 6 concludes that matter as such does not exist except as an idea in the mind.

According to Berkeley, belief in the independent existence of matter—related to the adherence to abstract thought—has contributed to confusion and error in modern philosophy, resulting in a skeptical questioning of the reality of the world around us and the human ability to know things. If we eliminate the existence of matter from our philosophy, many problems are solved, including how the body and the soul interact, the problem of evil, and the reliability of our sense perceptions.

Berkeley answers various anticipated objections in Sections 34–84, highlighting how his theory, unusual as it may seem, accords with common sense, science, and Christianity. In Sections 85 to 156, Berkeley concludes his treatise by returning to the question of God as the source of all things and the ultimate goal of philosophical inquiry, which is to lead to religious piety according to the precepts of the Christian Gospel.