Skepticism in Philosophy: Descartes, Chisholm, and Moore's Proof of an External World
Skepticism is a basic part of the Western philosophical tradition. It posits, at its simplest level, that human beings can never arrive at any certain knowledge about the world nor can objective truth ever be ascertained (Hooker, par. 1). While skepticism has a long history in Western civilization, its development took a crucial turn when Rene Descartes turned himself to the question of how we can know anything. Modern skepticism is a derivation of Descartes' examination of the nature of knowledge and man's relationship to it. However, Descartes has not been accepted without question. There are many philosophers who refuse to accept the basic tenets of skepticism, including the inability for anyone to possess objective knowledge of the external world. The skeptics claim that we know significantly less about the world than we presume to know (Steup par. 1). Notable among Descartes' detractors is the 20th century philosopher Roderick Chisholm who saw this issue as fundamental to any philosophical discussion (Faber par. 2). Chisholm developed his own counterargument to the Cartesian system. However, examined with a harsh, critical eye, it becomes evident that Chisholm's argument is ultimately flawed. Rene Descartes qualified the importance of skepticism to Western civilization; Chisholm's attempts to undermine that centrality have thus far proven ineffective.
In the era of the Enlightenment, Rene Descartes set out to reinvent the whole of Western epistemology. He began simply by questioning the very basis of all philosophical thought -- whether or not it is possible to actually know anything. His intent was to question whether or not it is possible to know anything, if truth can somehow exist external to the individual mind (Hooker par. 9). This is not as simple a query as one might assume. For those uninitiated in philosophical thought, it probably seems obvious that human beings can possess objective knowledge about the world. After all, we know that the sky is blue. We know that wood is hard. We even know that water is a molecule composed of two hydrogen atoms and one oxygen atom. But Descartes challenged all of this. He wondered to himself how we know that we know these things. What if the whole of the external world was an illusion? How would any of us presume to know the difference? Descartes recognized that human perceptions were not the most useful means for deducing the nature of the world. Senses can lie or be distorted. Memories will fade. It must have seemed to Descartes that all of human experience was designed to facilitate doubt in the veracity of the external world. After some deliberation, Descartes realized that the fact that he could doubt the world proved at least one thing: that is, that he himself was real or, as he phrased it, cogito ergo sum. This was the basic proposition upon which Descartes was able to formulate other true statements (Hooker par. 9).
Descartes laid the foundation for the Cartesian method of systemic doubt. While not generally characterized in these terms, it is nonetheless the basis for all scientific examination and thought. The system of thought that Descartes formulated was based on the exacting rigor of the question. Descartes recognized that we must continuously question all propositions. Skepticism, accordingly, demands that the individual be willing to doubt the whole of the external world around him or her. Propositions are tested then retested until one can arrive at a relatively true conclusion (Hooker par. 10). Since the time of Descartes this has been the basis of philosophical and scientific thought. Whether or not individuals realize or accept it, skepticism is the core of Western philosophy. It recognizes that the world is inherently unknowable. The best we can accomplish with any certainty, Descartes established, is that the individual subjective mind is real. All other propositions built up from this as true are subject to doubt and questioning. Unfortunately, as is not surprising, skepticism has not always gone over well with other philosophers.
Many have a problem with skepticism because it is vigilant in its attack on our ability to know anything objectively. Common sense suggests that we do know much about the external world. People want to believe, in essence, that knowledge is somehow sacrosanct and objective to human experience. It can be known and probed and understood -- knowledge, by this regard, is simply out there waiting to be found. Descartes undermined this assumption and challenged all minds to never accept the world as anything but possible propositions. Doubt is the greatest tool of the thinking mind according to the Cartesian system. At issue is our ability to distinguish genuine from purported knowledge (Faber par. 3). Philosophers such as Roderick Chisholm have placed this question at the heart of all discussions of Western philosophy.
Chisholm was never satisfied with Descartes skepticism and its conclusion that the external world can never be known with absolute certainty. For Chisholm the problem was simple. We must answer two questions: (A) what do we know? And (B) what are the criteria of knowledge? While that seems easy to do, Chisholm has qualified the issue aptly -- neither (A) nor (B) can be adequately answered without first answering the other (Faber par. 7). In other words, it is impossible to identify what we know without first establishing an epistemology. Unfortunately, it is also impossible to develop such an epistemology without first having some knowledge to work with. Chisholm suggested three solutions to this problem in knowing: skepticism, methodism (which answers (B) before (A)), or particularism (which answers (A) before (B). He rejected the first because he felt it was apparent that we did know things about the external world. He rejected the second because he felt that any system of thought that did not flow from existing knowledge was arbitrary and limiting. Chisholm settled on particularism despite the inelegance of the solution; he simply couldn't bring himself to accept skepticism at its face (Faber par. 11-15).
Chisholm's particularism can be seen in practice in G.E. Moore's famous attempt to prove the existence of an external world. When asked to demonstrate the existence of that world, Moore raised his hands and stated plainly that here were his hands (Steup par. 16). While glib, this answer nevertheless mirrors Chisholm's rejection of skepticism. Moore asked his audience why they shouldn't use the existence of their own bodies as proof for the existence of a world external to the individual mind. Unfortunately for the opponents of skepticism, this is a wholly ineffective argument against skepticism. Moore was, in effect, question begging. The skeptics assert that knowledge is unachievable. One cannot undo this assertion simply be stating that one has achieved knowledge. While it is perfectly fine to say so, this is not a rational argument and does little to refute Descartes basic premise that the external world cannot be known.
In fact, this is the basic flaw in Chisholm's argument, one that was also present in Moore's supposed proof of an external world. Chisholm found skepticism unappealing because he presumed that human beings already possessed knowledge about the external world. For that reason, Chisholm reluctantly labeled himself a particularist. But this is a flawed argument. From an intellectual standpoint, there is nothing unappealing or unjustified about the skeptic's argument. One would only find the premise unappealing if one were already tacitly a particularist (Faber par. 18)! In other words, Chisholm had made an assumption about his ability to know even before he began to examine the question of whether or not human beings could know anything. Coming into the matter with faith in the belief that knowledge is attainable, Chisholm naturally gravitated towards an epistemological solution that permitted that faith. He rejected skepticism not because of any logical or…