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\author{David Golombek}
\title{Descartes' Dream Argument}
\date{\today}
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Descartes' argument that no one can ever truly know anything is one of the most counter-intuitive arguments that can be imagined, but also one of the most difficult to logically disprove.  It is a destructive argument, in that it merely shows that other ideas and beliefs are unsound.  Unfortunately, this means in most cases that in order to disprove the argument, one must create a constructive argument, building from the ground up.  Thus, I shall attempt to tackle the argument in two ways.  First, I shall attempt the classical counter-argument of building up a base of true knowledge from the ground up.  Second, I shall attempt to circumvent Descartes argument by modifying his qualifications for knowing something.  However, before doing either, I shall summarize the points that Descartes brings up in his argument, in order to show the contrast between them and my arguments.

Descartes argument is actually quite simple and may be summed up quite quickly.  In order for anyone to know anything about the external world, they must know that they are not dreaming.  However, it is impossible for anyone to tell whether or not they are dreaming.  Thus, no one can know anything about the external world.  The first statement is trivially true, for it is impossible to trust any information obtained through a dream.  Although one might actually subconsciously learn or realize something during a dream, it is not until one wakes up that he can truly know the information.  The second statement is true for most people, although there are a few people who can tell the difference between the waking and sleeping.  This is based on the concept that they have at one time been awake, and thus falls through as a counter-argument.  Because the two premises of Decartes argument can easily be shown to be true, the logic may be said to be sound.  Likewise, the conclusion follows directly from the two premises, and thus the entire argument is valid.  I have already stated that I find the argument implausible, and thus I will begin to rework the topic, hoping not to encounter the same problem as Descartes.

Everything I think I know, I have learned through my senses.  I have no inherent knowlegde of anything, and thus have learned eveything I know from sensory input, or deduced it from this inupt about outside world.  Thus, all my knowledge is dependent upon the setup that is delivering input to my brain.  Do I necessarily have to doubt all that which has come in through my senses, as Descartes supposes?  He questions the reasonableness of trusting one's senses, first on the grounds that they occasionally deceive you, and secondly on the basis of ``being a man who dreams''.  Since we don't know if we are asleep or awake, we can't trust our senses.

In his next meditation, Descartes comes to the conclusion that we can know that we exist, due to our questioning of our own existence.  Since we exist at times when we are questioning our existence, and we can do so continuously for a period of time, we can thus prove the concept of memory, because we know we have existed at two distinct points in time.  If one is to suppose that the evil demon is responsible for our memory of the previous state of existence, then it is just as reasonable to speed up this process so that in no time scale can we remember our own existence.  Descartes has given, and we in class agreed, that we do indeed know that we exist, so the evil demon must not be continually deceiving us.  There must be some level at which we know we exist, if merely from thatfact that we are being deceived.  It is therefore necessary that we have some sense of memory.  Once we can trust our memory, it is possible to evaluate what we think is the world around us, meaning that I can compare my memories of senses to what I am currently sensing.  In evaluating my memories, I find that they are consistent over time, with gradual changes that can be accounted for by the passage of time.  While objects do not stay the same, their changes may be broken up into intervals of time wherein the changes are easily traced, as Locke does in his definition of the physical body theory.  Thus, whatever mechanism, be it a dream or an evil demon, is feeding the input to my senses, it is consistent.  This is in direct contrast to what I currently take to be my dreams, which are rarely consistent for extended periods of time.  Whatever sort of dream is in charge of providing input for my life, it must be radically different than those I encounter every night.

In what I take to be my waking world, I expect events to happen in an orderly manner.  When I see an object, I expect it to remain unchanged, or to change in a reasonable manner.  There are occasional cases in which I am temporarily deceived by my senses, but in all such cases, I can reproduce the effect.  Where Descartes takes a one time failure to be sufficient reason to mistrust his senses, I feel that if my senses can be tricked in the same way multiple times, it is merely a fault in my body that I must be careful to take into account.  Thus, I have no reason not to mistrust my senses.  Events follow other events in a sensible order, meaning that even if I don't know the exact logic of them, I can reproduce happenings that lead to the same results.  In my dreams, quite oppositely, events happen in random order, without respect to prior occurrences or contradictions inherent in their order.  Again, what I have every night as dreams must be different in character to the dream that is controlling my life.

Unfortunately, what I believe to be my dreams may or not be similar to the dream that is providing input to my brain.  Indeed, the overall dream would have to be perfect in all respects, especially with respect to memory.  But what then is it too distinguish between it and wakefulness?  What I take to be wakefulness contains those qualities necessary to actually know about the world around me, in that my reasons for believing things to be true are incompatible with those things being false.  Since all my memories tie together in a way I feel is logical, I can then expect future events to unfold in similar manner.  Although this is not a solid proof to base future logic upon, it is a strong enough proof to use as a reason to treat the world around me as my waking world.  Even if I'm not 100 percent positive I'm not dreaming, I can still reasonably expect events to continue occurring in the same regular pattern as they have for the first eighteen years of my life.

Unfortunately, the above argument is not perfect, and thus I will attempt to tackle Descartes problem from another angle.  Descartes sets as a requirement for someone to know something that they must know that it is certainly and indubitably true.  This entails that all the evidence you have for that thing being true conclusively proves that it is false.  We have seen the problems this view entails, mainly that it becomes impossible to know that anything is true.  So, one must weaken this requirement in some way in order too be able to know things.  However, if one does so to far, the replacement criteria becomes unconvincing.  We discussed two possibilities in class, one based on probability of knowing something is true, and the other on the fact of something being true causing you to know it is true.  The first of these, as stated, is far too weak, as it is easy to make many counterexamples where probability is flat wrong.  The second is simply to vague and undefendable to be accepted.  Thus, I offer the following as a replacement.  All my evidence for T is inconsistent with T's being false, on the condition that T follows the same rules as all previous occurrences.  This may seem to beg the question, as it reduces this case to the one previously dealt with, and that is true.  However, this is also the strongest possible replacement, because it is the same as the original in all cases that one would hopefully ever encounter.

This unfortunately brings us back to the problem that I still can't guarantee that the future will behave the same as the past, nor that I really know everything that has happened in the past.  It does at least give me a base so that I can live on from day to day, as I have done before doubting that I knew anything.  It may be impossible to completely diprove Descartes proposition, but now at least I have a solution that I can reasonably live with.  Thus, I conclude that Descartes argument is a good one from a logical point of view, but a poor one from a realistic point of view.

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