Knowledge and Reality: On Skepticism

I.

Questions about the nature of the physical world are among some of the oldest and most prominent in philosophy. Such problems challenge our most basic beliefs about the structure of the world and force us to reconsider everything we think we know. How do we know that we are not dreaming, or in The Matrix? For that matter, how do we know there is a material world at all, and that we are not simply immaterial minds whose ideas create our perceptions? In this essay I will address skeptical questions such as these by comparing a simple skeptical argument with G. E. Moore’s famous counterargument. I will attempt to demonstrate that the skeptical argument is in fact the more reasonable by considering several flaws in Moore’s reasoning.

II.

Before looking at Moore’s argument, we must first consider the skeptical argument to which he is responding. Though there are numerous ways in which to present this argument, we will consider a simple version for example purposes.

Skepticism can be defined as “The position that denies the possibility of knowledge”[1]. A skeptic of the material world questions what we can know, with absolute certainty, about the nature of existence. At first, it may appear that we know plenty about the world we live in, but upon further consideration, we realize that many of the things we �know’ to be true are not absolutely certain – we don’t �know’ them for sure. In his Meditations on the First Philosophy Rene Descartes undertakes a famous thought experiment, questioning what knowledge he has at the most basic level:

Whatever I have up till now accepted as most true I have acquired either from the senses or through the senses. But from time to time I have found that the senses deceive, and it is prudent never to trust completely those who have deceived us even once…there are many other beliefs about which doubt is quite impossible, even though they are derived from the senses – for example, that I am here, sitting by the fire, wearing a winter dressing gown, holding this piece of paper in my hands, and so on. Again, how could it be denied that these hands or this whole body are mine?[2]

It might seem that such basic things, such as having hands and a body, or knowing where you are in a particular moment, could be absolutely knowable, but Descartes continues to question various possibilities:

How often, asleep at night, am I convinced of just such familiar events – that I am here in my dressing gown, sitting by the fire – when in fact I am lying undressed in bed!...As I think about this more carefully, I see plainly that there are never any sure signs by means of which being awake can be distinguished from being asleep…Suppose that I am dreaming, and that these particulars – that my eyes are open, that I am moving my head and stretching out my hands – are not true. Perhaps, indeed, I do not even have hands or such a body at all.[ 2]

And thus Descartes comes to a surprising realization – that it is impossible to prove, with absolute certainty, that our sense perceptions give us an accurate depiction of the world, In fact, there is a possibility that the physical world does not exist at all.

III.

In 1986 notable philosopher John Pollock published a paper asking people to consider the possibility of what he described �the brain in a vat’[3]. He asked his readers to imagine a situation where their brain is removed and connected to an incredibly powerful and complex computer. This computer monitors brain activity and supplies it with electrochemical impulses to stimulate the senses. To the owner of the brain it appears as if they are simply going through life as usual, however, their sensory stimuli are not being supplied by interaction with the real world, but by the computer. Such a person would have basic beliefs about the world, such as where they currently are, or that they have arms and legs, that are false. A possible argument for skepticism can be formulated from this possibility:

1) I know I have hands only if I know I am not a Brain in a Vat

2) I do not know that I am not a Brain in a Vat

3) I do not know if I have hands.

This seems to be a startlingly conclusion – of course we know that we have hands. Such a conclusion cannot be put forward without some resistance, perhaps the most of famous of which was provided by G. E. Moore in his 1938 paper “Proof of an External World”[4].

Moore’s argument is based on simple common sense, and provides an interesting response to the skeptical position.

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