Stroud, a contemporary philosopher, argues that part of Descartes’ work in the 17th century largely initiated a still ongoing philosophical problem of skepticism: how are people able to say that they know anything about the world around themselves? This is a very particular type of philosophical skepticism, in that it addresses only one’s knowledge in regard to the external world itself, and not the far more broad possibility for knowledge about anything whatsoever. Descartes in particular held one truth to be self-sufficient and therefore certain above all others, “I am a thinking thing,” necessitating at least one’s internal existence of the mind, and it is from this position that he begins to question what else one may come to know. Although he and others following him have provided powerful arguments in favor of knowledge in regard to the world external of oneself being grossly inaccessible, many popularly raised objections have failed to properly address this problem correctly, lest it have been successfully put down over the millenia, or prevented from creeping its way in to every other branch of philosophical discussion. Stround claims that a successful reading of Descartes’ argument entails that we necessarily can not know about the external world at all, and so that any objections which accept the validity of the way in which he proposes his admittedly compelling skeptical question are always going to fail.
Descartes begins his project by reflecting on everything he has ever previously been told, and attempting to deduce which of these claims can be found absent of doubt. He provides examples from his own past where he has strongly believed in things which later turned out to be clearly false, and these are definitely not the sort of claims from which we can have any hope to build the rest of our system of knowledge on. Centuries later, there are still many major misconceptions held by large segments of the public, as in regard to how such contagious diseases like the common cold are spread, and these are certainly not absent among the well-educated either. However often these sorts of misinformative tales are told, it is always possible to subject them through a rational analysis: Have we observed the conditions we affirm to necessitating being inflicted with the cold having been fulfilled successively in people across time? If not, how much can we trust the people who compel us to believe that these conditions are still the case despite a lack of prior personal observation? Are our instructors random persons found on the street, or practicing doctors? Can even every practicing doctor be trusted to act entirely without ulterior motive? Not being a doctor and possessing their accompanying vast background in medical knowledge myself, why should I ultimately trust any single thing I’ve ever been told to know about some complex disease on its own?
This sort of critical method is exactly what Descartes hopes to carry out in regard to what will be any sort of foundational knowledge about the world that is able to persist in spite of his prior skeptical conclusion. Certain and distinct truths will make for fulfilling accounts in response to any such battery of doubts ever aimed at them, and so this is also a pragmatic project that has always been played out by the human mind, but which he has worked to clarify: beliefs which have been made more certain through careful investigation and good reasoning are always preferable.This process would take far too long to subject each individually held belief through it in its entirety however, involving potentially infinite chains of questioning. Instead, Descartes attempts to deal with entire classes of beliefs at once, such that if they can all be cast under the same doubt, they could also all at once be tossed aside in search of truths free of any doubts. It seems that people would be able to come to know very little about the world around themselves without the use of any of the senses. The blind make up for their handicap through extending their use of the other senses in making observations about the external world. Although the senses share in this form of apparent stunning contribution from the world, can they altogether be subjected to any general doubts? We are sometimes misled by our senses as to the way the world really is, as in the case of seeing something blurred from a distance into an irregular shape. This is not in itself enough to cast doubt on the senses altogether, which appear far more often to be correct, as this would deny even the possibility to provide a successful account for the conditions which lead to these inconsistent cases in the first place.
In the scenario Descartes provides, sitting comfortably in a well-lit room without anything that might work to obscure his vision, he always finds himself left with doubts as to the actual nature of the things as they appear before him, provided by the senses. By comparison, any other instance of normal observation followed through with much weaker forms of investigation could only result in less reliable reports being gathered. Even in this very best representational case, it seems entirely compatible with a situation where he is experiencing all the same phenomena, only now occuring within a dream, leading us to question whether we can ever be certain of the things our senses are telling us do come from the outside world. The only way we are able to measure the world around us is by the senses, and it is clear that they are entirely unreliable as long as we happen to be dreaming. In every case where we believe we have been led to know something about the world around us by the senses, there is then no test we could employ in order to determine whether this is taking place while in a state of wakefulness or rather in a state of dreaming, and it is here that Descartes’ problem of skepticism in regard to the external world surfaces. Even if we happen to be dreaming exactly the state of affairs which surrounds our sleeping body through arbitrary chance, this is no different than guessing coin tosses correctly, and is not at all a good reason to say we have come to know something. Because this is a condition which casts doubt against every belief we may hold about the world around us in any given moment, we should then always refrain from saying that we know anything about the external world.
It is of course always possible that one could be dreaming while they believe themselves to be awake, but this does not on its own seem like enough to deny that we can know anything about the external world altogether. In the first place, we can only discuss the notion of dreaming in so far as it is a response to the things in the outside world which we experience while having at some time previously been awake. Knowing that you’re not presently dreaming is not required to know that you receive generally reliable sensations. Rather, these reliable sensations are first necessary in order to gather the internal ideas which result in any of the coherent experiences we could ever have while later dreaming. If we accept Descartes’ condition that not dreaming is a condition of knowing anything about the world, there is certainly no way that we can proceed. Any test we use will be determined through results provided by the senses, which can never be made certain given that we might be dreaming them. Instead, we should deny this condition, and question whether Descartes can be dreaming in the situation that he presents at all. If this really was supposed to be the representative case for the senses providing useful information about the world around us, then it is also exactly the case wherein we could ever hope to say we are not finding ourselves dreaming. We would like to say that we know many things throughout every day without stopping to consider whether we are dreaming or awake at each and every one of these moments, along with the accompanying infinite list of other equivalent considerations which might equivalently work to account for a situation. Rather, it must not be the case that we should satisfy every single incompatibility in order to know something in otherwise ordinary circumstances. This wrongly leads us to determine that we can never say things are true of the world around us in just the same way that it is wrong to suggest exceptions to the reliability of the senses for which we’ve already provided the conditions behind occurring should lead us to rule their reliability out altogether.
As Descartes would have it, knowledge would amount to a neat, consistent mapping, with foundational truths leading nicely and unambiguously to their more complex relations. This is never actaully the case during the course of ordinary human learning, as even in the field of mathematics, which seems like a best representational case of a web of interconnected knowledge, founded on a list of well defined axioms, all highly acclaimed mathematicians today delve in to very specific branches of research and are not nearly as well informed in others. Given this conception of knowledge, one would at first have no understanding of mathematics, be explained its list of basic axioms, and thereby come to know the entirety of everything else they possibly entail. Our dreaming will always possibly be incompatible with our having a normal experience in a room by the fire, and so there is no test by which this knowledge condition could be overcome. However, in order for there to be the possibility that we would come to know that we are having an ordinary experience as opposed to one occuring in a dream, as in the case of Descartes really sitting by the fire, we can suppose that we should not have to meet this strict condition. This leaves open the question of what all knowledge about the external world could even be said to share in common, if not at least that it is always certainly formed while in a waking state. Still, a correct negative analysis would seem to suggest that we do not always need to field every single doubt in regard to each belief before we can say that we know it, only that we must contend with the doubts we are immediately presented by before we can conclude we’ve performed some reasonable enough investigation.