John Locke (1632-1704 c.e.) and Bishop George Berkeley (1685-1753 c.e.)

What do we mean when we call someone a “skeptic?” We mean it’s hard to convince them to believe something that other people are likely to believe. When someone is gullible they are not skeptical. There are levels of skepticism; skepticism is a continuum. At one end is the skepticism that Descartes used: systematically doubting (being skeptical of) everything. At the other end is very light skepticism where much is accepted but certain things need verification.

Keep in mind that we are in the realm of epistemology, the theory of knowledge. How can we know things and how well can we know them? How skeptical should we be about the things other people tell us? These are epistemological questions. Epistemology, remember, is one of the pirmary divisions of philosophy.

On our way to skepticism, we will first take a look at empiricism, the idea that all ideas and knowledge can be traced back to experience. How do we know that fire burns wood? Because we have seen fire burn wood. For the empiricist, this knowledge resulting from direct experience is supreme.

There are three famous empiricists and they were all British—hence, these figures are known as the British empiricists. The first empiricist we are studying is John Locke. Like Descartes, Locke wanted to understand our ideas and our minds in a way that went against the focus of that of previous philosophers only interested in metaphysical issues. Locke wanted to know more about the very process by which humans gain knowledge.

Locke thought that our abstract ideas of things like cubes, circles, spheres (etc.) comes from our experience of actual objects. For instance, our idea of cube can be extracted from our experience of objects with a cube-like shape--such as gamecubes and dice.

What is the sound of one hand clapping? Here's Bart's answer...


John Locke

For Locke, every idea comes from a sensation. We have an abstract idea of “cube” in general because we’ve seen plenty of cubes in our lives—dice and Nintendo GameCubes, for example. Locke also said that ideas are copies of things we experience. So if you go outside and a see a tree, your idea of that particular tree later will be a mental image, a copy, of that original tree.

Thus, for Locke, we know something is true if it can be traced back to experience. If I say, “Some apples are red,” I know that it’s true because I see a red apple on my kitchen table. It is indeed true that at least some apples are red since I can see at least one apple and it is red. This is also known as “The Correspondence Theory of Truth.” This theory holds that an idea is true if it can be traced to experience. Another theory is coherence: the coherence theory says that ideas can be evaluated in relation to other ideas that are already established as true, innate ideas. But this theory clearly butts heads with the correspondence theory which says that there are no a priori truths. It’s good to keep in mind here that Locke’s inclination to lay the stress on experience came from his working as a physician: he saw that knowing how to help people depending on his experience with previous patients.

This leads us to Locke’s rejection of innate ideas. He thought that Descartes and other rationalists, in their attempt to create a foundation for knowledge that eradicated dogmatism, only created a different dogmatic system. For who decides what knowledge is innate and what is not? Famously, Locke thought that the mind is a blank-slate (“tabula rasa” in Latin). In other words, he thought that we are all born with no knowledge, no innate ideas, and we look to experience to learn everything. Does this sound right to you?

Locke also advanced something called “substance,” something from which our ideas arise, something that underlies all mental process. Locke thought that there was an underlying substance in physical things (matter), but he thought that the substance underlying mental processes was different (mind). Just as the redness, roundness, and smoothness of an apple refer back to the substance of the apple (matter), so worrying, thinking, planning (etc.) refer back to the substance (mind). In other words, Locke believed in a sort of Cartesian dualism.

Locke made a distinction between qualities that exist in objects and qualities that exist in people. This is a distinction between objective (things out there in the world independent of people or knowers) and subjective (things that depend for their existence on knowers). Qualities that exist in objects are primary (shape, location, etc.) and qualities that exist in the knowers are secondary (color, taste, etc.).

But, you might be wondering, how can we know that primary qualities even exist according to Locke’s system? Locke thinks that all knowledge comes from ideas that can be traced back to experience. So, secondary qualities clearly exist. The color red, for example, can be traced back to the apple. But primary qualities exist independent of the knower, so how can we trace them back to experience if the knower does not experience them? This brings us to an even greater concern: if all I know are my own experiences, how do I know that an external world even exists? This is, indeed, an inconsistency in Locke’s philosophy. While he did a lot to show the significance of empiricism and the way we form ideas, he wasn’t quite ready to follow the formulations of his own system to their conclusions.

George Berkeley

What’s the sound of one hand clapping? If a tree falls in the forest and no one is around to hear it, does it make a sound? These are proverbial philosophy questions, one of which comes from Bishop George Berkeley (UC Berkeley is named after him). Does anyone remember Bart Simpson's answer to these questions? I can’t remember the episode, but Lisa poses the question about the hand clapping and Bart responds by hitting the fingers of one hand against the palm of the same hand. As funny as a such a response is, it’s not the sort of response Berkeley had in mind when he posed the question about the tree falling.

Berkeley said no—a tree falling in the forest does not make a sound if no one is there to hear it. This is because Berkeley completed denied the existence of an external world. He recognized the flaw in Locke’s system and took the stance that ideas are the only things that exist: this is known as “idealism.” What do we know except ideas? Berkeley challenged the notion that ideas can be traced to objects in the world. He reasoned that since things are constantly in flux, constantly changing, no idea can be traced to any concrete thing. We do not perceive things as they are but rather things as we perceive them. There is nothing else. In a similar way to Descartes, Berkeley eventually invoked the existence of God to “prove” that an external world exists.


Berkeley believed that there is really no external world and that the world is only a collection of ideas in our brains. A little bit scary, isn't it?

Copyright © Luke Cuddy 2008