John Locke’s and Rene Descartes Opinion on Human Conceptions and Knowledge

Introduction

How can we know if we are a brain in a vat? Can we be sure that we are not the playthings of evil demons? These questions have been discussed by many philosophers in the past, and still, we do not have proof that we are not some demon's plaything. Yet, at least two prominent philosophers, René Descartes and John Locke, believed there are ways to prove that we are not brains in vats.

René Descartes' Perspective on Knowledge and Existence

At one point in his philosophy, Descartes reflected that perhaps God or some evil spirit was constantly tricking his mind, causing him to believe what was false. Descartes then responded to this argument by beginning with the observation that even if he were dreaming, or constantly deceived, he could at least be certain that he had thoughts, and therefore existed as a thinking being. If an individual has an idea, then that individual would understand it and assent to its content. If, as Descartes claimed, I am born with the idea of God, who embedded that idea in me at my creation, then my understanding of what God is should conform to that idea. Thus he wrote, the idea must be a "clear and distinct" perception of the mind. Nothing could make him doubt it.

Furthermore, in Discourse on the Method, Descartes introduced the famous Latin phrase cogito ergo sum, which means "I think, therefore I am" (Descartes, 1637). Descartes then argued that cogito ergo sum has passed the test for the method of doubt because he cannot be mistaken in his beliefs about the way things seem to him. Descartes held that by means of reason alone, certain universal, self-evident truths could be discovered, from which the remaining content of philosophy and the sciences could be deductively derived. Descartes therefore believed that his knowledge exists.

Descartes then tried to prove the existence of God, which would help him in proving knowledge. He thought that the representative power that a finite thinking object has in creating mental pictures of things that are more perfect than itself cannot come from itself; it must somehow be derived from something at least as perfect as the objects represented by the thinking thing. It follows that the representative capacity that finite thinking substances, like ourselves, have in making a representation of an infinitely perfect being would ultimately have been derived only from an infinitely perfect being. Therefore, from the fact that finite beings can frame the idea of an infinitely perfect being, it can be inferred that an infinitely perfect being, or God, must exist.

Here is the argument that Descartes gave:
(1) I am able to form an image that is more perfect than myself, and therefore it must be derived from something at least as perfect as the image that I had formed.
(2) The perfect image that I formed must be from the most perfect being.
Therefore, God must exist because an imperfect person is able to form a perfect image.

However, the argument Descartes gave was circular because Descartes uses his power of reason to establish a condition without the use of reason, which made the argument unjustified and untrustworthy. As a result, Descartes was not able to refute the skeptic's argument.

John Locke's View on Knowledge and Existence

On the other hand, Locke begins his philosophical examination of knowledge by trying to refute the claim that some of our knowledge is original, in the sense that it comes from ideas which are innate or inborn. Locke started his refutation based on a doubtful assumption: If I have an idea, then I would understand it and agree to its content. Locke believed that the only way that ideas could arise is from sense experience. We form ideas as the action of physical bodies on our own bodies. As Locke points out, sometimes he uses 'idea' to refer to the end product, what exists in the mind, and sometimes he uses it to refer to the quality in the body which causes the idea. Locke classified ideas as simple and complex. All complex ideas are said to be made up, ultimately of simple ideas, and their complexity is the work of the mind (Locke, 1690).

Locke made the further claim that our ideas of primary qualities resemble the qualities, while those of the secondary do not. Berkeley will raise the question of how Locke can make any claim of resemblance, given that he has no data other than the ideas themselves, and hence cannot compare them to their supposed originals. Locke seems to have held the resemblance view because he could not conceive of bodies any other way.

Locke also focused on the question of our knowledge of the existence of things. That we know our own existence intuitively is based on an appeal to the argument of Descartes, that doubting one's own existence presupposes the existence of a doubter, and hence is futile. This knowledge is perceptive, it seems, because one can hold this thought in its entirety at a single time.

Like Descartes, Locke also tried to prove the existence of God. His argument is like this:
I exist.
Because nothing cannot produce anything, there has to be something since eternity.
And the thing must be all-knowing and powerful.
Therefore, there must be a God because it created me.

Locke's argument about God seems weak because this conclusion is quite dubious on the grounds that the only thing he needs is the existence of himself. But even if he evokes this being as the cause of the existence of the world, then the being only needs to be as powerful as it takes to produce the world. Moreover, the argument also gave the impression that the properties of a God seem to surpass what is required to explain the world around us.

Furthermore, Locke tried to connect his theory with the existence of God. He says that he "has reason to rely" on the testimony of the senses. He thinks that since God has given him these faculties, and they are correlated with the production of pleasure and pain, Locke tried to refute the skeptical argument, but in the four reasons that he gave in the argument, he was not successful in defending his ideas since he cannot prove what the exterior cause is.

Conclusion

Even though Descartes and Locke had tried to prove that we are not brains in vats, neither philosopher has succeeded. Both Descartes' and Locke's arguments were missing a justified belief, which is crucial for knowledge. As of now, we are still unable to claim that we are not brains in vats. Hopefully, with more philosophers gathering their minds together, we might have an answer to this unanswerable question.

References

Descartes, R. (1637). Discourse on the Method.

Locke, J. (1690). An Essay Concerning Human Understanding.