A Treatise Concerning the Principles of Human Knowledge (1710) Informative Summary


Berkeley’s “A Treatise Concerning the Principles of Human Knowledge” is a seminal work in Idealism. It challenges the prevailing notion of Materialism, arguing that the belief in a mind-independent material world leads to skepticism and impiety. Instead, Berkeley proposes that reality is composed of minds (spirits) and the ideas they perceive.

He argues that sensible qualities, like color, shape, and motion, are merely sensations existing within the mind. They cannot exist independently of a perceiving mind. The existence of God, as the ultimate perceiver and source of ideas, is therefore crucial to Berkeley’s system, guaranteeing the stability and consistency of the world we experience.

Key Findings:

  • The Impossibility of Abstract Ideas: Berkeley critiques the notion of abstract general ideas, arguing that we can only conceive of particular things.
  • Esse est Percipi (“To be is to be perceived”): Berkeley’s famous principle encapsulates his argument that the existence of things depends on their being perceived by a mind.
  • God as the Ultimate Perceiver: To avoid the implication that things cease to exist when we don’t perceive them, Berkeley posits God as the ultimate perceiver who guarantees the continued existence of the world.
  • The Natural Immortality of the Soul: As the soul is an active, indivisible spirit, it is not subject to the same laws of decay and dissolution that govern material bodies.


  • The Nature of Reality: Berkeley challenges readers to reconsider their understanding of what constitutes reality. He argues against the notion of a mind-independent material world, proposing that reality consists solely of minds and their perceptions.
  • The Limitations of Language: Berkeley explores how language can mislead us into believing in abstract ideas, highlighting the importance of clear and precise thinking.
  • The Importance of Perception: By emphasizing the role of perception in constituting reality, Berkeley encourages readers to examine the relationship between their senses and the world they experience.
  • The Role of God: Berkeley’s philosophy places God at the center of his system, arguing that God’s constant perception ensures the stability and consistency of the world.

Historical Context:

Published in 1710, Berkeley’s “Treatise” emerged during a period of significant philosophical and scientific advancement in Europe. This was the era of the Enlightenment, characterized by an emphasis on reason and empirical observation. While Berkeley shared the Enlightenment’s commitment to reason, he challenged the materialistic tendencies emerging within the scientific revolution, particularly the view of the world as a purely mechanical system governed by deterministic laws.


  1. Sensible qualities exist only in the mind: Objects are collections of ideas perceived by the senses, and these ideas can only exist within a mind.
  2. There is no material substance: Berkeley denies the existence of a mind-independent material substratum that supposedly supports sensible qualities.
  3. The mind is active, not passive: The mind is not a blank slate passively receiving impressions from the external world but an active agent that perceives and wills.
  4. We have no idea of spirit: As spirits are active, there cannot be a passive idea that represents them.
  5. God is the cause of our sensations: Since ideas cannot cause each other, and humans don’t cause all of their sensations, the source must be a divine spirit.
  6. God is known as certainly as any other mind: The existence of God is evidenced by the order and regularity of the natural world.
  7. Nature is not a separate being from God: Attributing causality to “Nature” is just a way of avoiding acknowledging God’s direct involvement.
  8. Miracles are real events: They are not illusions but actual changes in the perceivable world brought about by God’s intervention.
  9. The soul is naturally immortal: As a simple, indivisible substance, the soul is not subject to the laws of decay and dissolution that govern material bodies.
  10. Abstract ideas are impossible: We can only conceive of particular things, not abstract general notions.
  11. Numbers have no abstract existence: They are signs that represent particular collections of things.
  12. Finite extension is not infinitely divisible: We cannot perceive an infinite number of parts in any finite object, so it’s illogical to say they exist.
  13. Geometric demonstrations are about universal ideas: This means the particular figures in a diagram stand for countless others of different sizes.
  14. Motion is always relative: It requires the conception of at least two bodies whose position in relation to each other changes.
  15. There is no absolute space: The idea of space is derived from our experience of the resistance and movement of bodies.
  16. Language can be misleading: The tendency to associate each word with a distinct abstract idea leads to confusion and errors in thinking.
  17. Final causes are worthy of study: Understanding the purpose and design of natural things is a legitimate philosophical pursuit.
  18. The study of nature should continue: Observation and experimentation are valuable for understanding God’s design and for practical benefits.
  19. God’s existence is evident to those who pay attention: The magnificence and order of the natural world clearly point to a divine creator.
  20. Atheism is a result of negligence and inattention: A clear understanding of God’s omnipresence and justice would make persistent immorality impossible.


Berkeley’s “Treatise” does not rely heavily on statistics. Its arguments are primarily philosophical and based on reasoning rather than quantitative data.


  1. Idea: The immediate object of perception, whether sensory or imagined.
  2. Spirit: An active, indivisible substance that perceives ideas and wills.
  3. Material Substance (Matter): The supposed inert, senseless substratum that philosophers believed supported sensible qualities.
  4. Esse est Percipi: Latin for “To be is to be perceived.” Berkeley’s famous principle encapsulates his belief that existence depends on perception.
  5. Abstract Idea: A general notion supposedly formed by mentally separating out common features from particular things.
  6. Natural Philosophy: The study of the physical world, equivalent to what we now call physics.
  7. Mathematics: The science of quantity, encompassing arithmetic and geometry.
  8. Infinitesimals: Infinitely small parts, a concept debated by mathematicians of Berkeley’s time.
  9. Occult Qualities: Unexplained powers or properties attributed to things, often used to explain natural phenomena before the rise of modern science.
  10. Attraction: The tendency of bodies to move towards each other, a concept used in Newtonian physics.


  1. The Apple: Berkeley uses the example of an apple to illustrate that what we perceive is a collection of ideas (color, taste, smell, etc.) and not a mind-independent material object.
  2. The Burning Finger: The pain we feel when our finger is burned is not caused by the fire itself but by a spirit, ultimately God, who produces the sensation in our mind.
  3. The Dream: Dreams demonstrate that we can have vivid sensory experiences even when there are no corresponding material objects present.
  4. The Watch: The intricate mechanisms of a watch point to an intelligent designer, just as the complex workings of nature point to God.
  5. The Blind Man Made to See: A blind man who gains sight would not initially perceive distance and external objects as we do, suggesting that our perception of the world is learned through experience.
  6. The Motion of the Earth: We do not directly perceive the Earth’s motion, but we can infer it from astronomical observations and the laws of nature.
  7. The Growing Plant: The upward growth of a plant seemingly defies the principle of universal gravitation, demonstrating that there are no necessary or immutable laws in nature apart from God’s will.
  8. The Tides: The rise and fall of tides can be explained by the gravitational pull of the moon, illustrating how a general rule can account for seemingly disparate phenomena.
  9. A Line Divided into 10,000 Parts: While we cannot literally divide an inch-long line into 10,000 parts, we can use it to represent a much larger line that can be so divided. This illustrates how geometric reasoning involves abstraction without requiring the existence of infinitesimal parts.
  10. The Resurrection: Berkeley argues that objections to the resurrection based on the identity of the body depend on the mistaken notion of material substance. If we understand “body” to refer to the perceivable form, then the resurrection becomes less problematic.


Berkeley’s “Treatise” offers a radical rethinking of the nature of reality, arguing that the world we experience consists solely of minds and their ideas. By dismissing the notion of material substance, Berkeley aims to eliminate skepticism and impiety, establishing a firm foundation for knowledge and religion. His philosophy, while challenging, compels us to examine our assumptions about the world and to acknowledge the role of perception and the ultimate dependence of all things on God.

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