John Locke, from England, and Irishman Bishop Berkeley were famous 17th-18th century empiricists. Being that these philosophers examined how one can know things, they were epistemologists, while propounding different metaphysical systems to explain their positions.
Locke felt that observation via the senses constituted the primary way one acquires information about the external world. Berkeley, on the other hand, felt that what one knows comes about as a result of one’s own ideas, rather than knowledge being based on an external substance. While both being empiricists, Locke would be classified as a materialist, while Berkeley is an idealist.
Locke’s Blank Slate and the Veil of Perception
Locke believed that the object of perception was an external substance. Each person when beginning their life possess’ a mind that is a Tabula Rasa or blank slate. According to Locke, when one is born there are no innate ideas, and therefore the information perceived is not based on rational principles, although reason does play a role in formulating knowledge.
Locke’s philosophy holds that there is a sort of correspondencebetween external things and one’s ideas. This correspondence leads to the supposition that Locke was a representational realist. Representational realism is the concept that one’s sensations contain a representation of the things being sensed.
For Locke, to perceive something external to the senses implies representational realism; otherwise how else can one know external corporeal substances? This representational realism led to what is referred to in philosophical circles as the veil of perception, that is things are not seen as they are in themselves. This is because there is a “veil” which one cannot penetrate, because the thing perceived exists independent of sensation. This concept had dire implications.
Berkeley’s Idealism: To Be is To Be Perceived
Berkeley, and idealist, criticized Locke. He considered himself to be a harbinger of common sense. He felt that Lockean materialism was flawed and resulted in extreme skepticism. With representational realism matter is never known as it is in itself, and this fact led to skepticism, because the question became how can someone know anything about the world at all, (e.g., external substances), if what one perceives is not a perception of the thing in itself?
According to Berkeley, the only thing that one knows are ideas. Berkeley claimed that something only truly exists when it is perceived. This is referred to in his dictum “to be is to be perceived” (e.g., esse est percipi). He believed that without something being perceived, one cannot say anything about it existing, or even say it exists at all! After all, he thought, the way one understands a substance is that it is something that exists independent of the senses.
If it does exist independent of the senses, how can one know the substance as it exists in itself? This leads to extreme skepticism according to Berkeley because one cannot know if matter indeed exists, since one doesn’t perceive matter directly (e.g., the problem of the veil of perception). For if something exists independent of the senses, then one is saying that one really doesn’t know anything about the substance as it exists in itself, (e.g., independent of the senses).
Berkeley solution is that one’s thoughts are composed of ideas, that substance cannot be perceived. The veil becomes an impenetrable blanket. Locke is defeated by this supposition by Berkeley that what one knows about the world are only ideas, that is one’s own ideas. Ultimately this brings up the problem that if one isn’t there to perceive it, does it cease to exist, since ones perceptions are only one’s own ideas.
Many are familiar with this philosophical paradox where if a tree falls in the forest and no one is there to perceive it, does it make a sound? If matter is simply reducible to ideas then when the ideas are not received one can’t say the event, in this case the tree, exists at all. Therefore there is no “falling” of the tree, and there can be no sound.
Berkeley’s Idealism and God
Berkeley ostensibly solves this quandary of whether things really exist by using his position on ideas as an argument for God. Berkeley was critical of Locke because God was not a necessary component of his philosophy.
For Locke, spirit is not necessary in the formulation of perception, where all that was important were external substances for perception. Berkeley replied to these perceived shortcomings of the veil of perception by saying that all things do exist at all times. They exist because God perceives everything in the world at all times, and therefore everything continues to exist always (e.g., as spirit). One philosophy professor of mine referred to this as “God putting ideas in our heads”.
In reference to Berkeley’s philosophy, Dr. Samuel Johnson once kicked a heavy stone and exclaimed, “I refute it thus!” Yet ultimately this refutes nothing (e.g., it could just be the “idea” of pain in kicking the “rock”).
The Empiricists An Anchor Book – Doubleday: 1961.
Honderich, Ted, ed., The Oxford Companion to Philosophy. Oxford University Press: Oxford 1995.