5.1.2.6 Moore’s Proof of an External Reality

That Idealism violates the tenets of common sense is its most glaring weakness, and G.E. Moore attacked this weakness relentlessly. More than anyone else, Moore recognized the deficiencies and logical problems associated with the forms of Idealism built into Berkeley’s claim that the external world didn’t really exist. He also took issue with Kant’s and Descartes’ theses that even if it did exist, we could never directly experience it, but instead constructed ideas or categories of understanding to interpret it. He countered Kant’s Idealistic position through a reaffirmation of objectivity and a revival of philosophical Realism. Although the scope of his writings goes far beyond the nature of reality, his contributions in this area are profound.

In his system, external objects are things whose existence is independent of our experience. These had been referred to before as “things in themselves” or “noumena”. They exist before us, continue to exist after us, exist when we are not looking, and exist when we are not aware of them at all. His goal was to demonstrate the existence of even one such object. By doing so, he would have proved the existence of an external world with that one object in it. If there is even a single external object, this opens the door for any number of external objects, and therefore an entire external universe of full of “things in themselves”.

Much of Moore’s work was in answer to Kant’s earlier work in Transcendental Idealism. It is a testimony to Kant’s tremendous range and influence that Moore dedicated himself both to overturning his Idealism, and also to finishing the work Kant began to establish the existence of an external reality that exists beyond our perceptions.

He famously re-invigorated the idea of “common sense” with respect to realism and gave a powerful common sense argument against Idealistic skepticism by raising his right hand and saying "Here is one hand," then raising his left and saying "And here is another". He concluded that since there are at least these two external objects in the world, he therefore knew that an external world existed.

To understand what Moore was trying to say, it’s important to differentiate between two very different issues. On the one hand is the issue of “the existence of an external world”, and on the other hand is “whether or not we can directly know that external world”. His demonstration of the raised hands addressed only the first of these two questions, leaving the second purposefully unanswered. In fact, he never successfully addressed the latter question.

Moore strongly believed that muddled thinking and imprecise language confused our thinking about reality. He thought that a combination of common sense and precise language were sufficient to address most philosophical questions. Because of the laxness in the use of language when addressing complex issues, philosophers exacerbate the complexity and create problems out of nothing.

His argument for reality utilizes the "denying the consequent" (AKA, "modus tollens") form of argument, which is a transposed version of the the modus ponens argument presented in the previous “Skeptical argument against reality” section:

• If a person doesn't know that reality is not an illusion, then that person doesn't know that external objects really exist


• That person knows that external objects really exist


• Therefore, that person knows that reality is not an illusion

What about the second premise above? Doesn’t it seem circular? Does it assume the conclusion in order to prove the conclusion? Not at all – He defended criticism of his argument in these words:

"I knew that there was one hand in the place indicated by combining a certain gesture with my first utterance of ‘here’ and that there was another in the different place indicated by combining a certain gesture with my second utterance of ‘here’. How absurd it would be to suggest that I did not know it, but only believed it, and that perhaps it was not the case! You might as well suggest that I do not know that I am now standing up and talking — that perhaps after all I'm not, and that it's not quite certain that I am!"

There is also another common sense, pragmatic explanation, although Moore did not use this argument: In the above example, he sees his hands extended. Everyone to whom he is demonstrating sees the same hands. They are all unanimous in their observations of the extended hands. Unless they are simultaneously dreaming the same dream, they are witnessing two real hands extended in actual space. It would be an enormous and highly unlikely coincidence if the dream explanation was correct, whereas it would be no leap at all to conclude that what common sense tells us is the right answer.

Moore’s most famous attack on Idealism occurred in an essay entitled "A Defense of Common Sense". In it he contended that the Idealistic skeptics could not give good reasons for us to accept their arguments. The defenses that the Idealist could muster were far less plausible than the reasons that could be presented to accept the common sense claims about our knowledge of the real world. In other words:

• There are only two options being considered:
1. there are no external objects or
2. there are external objects and reality is real
• Exactly one of (1) or (2) is true, but not both
• The arguments for (1) are very weak, and the arguments for (2) are very strong
• Therefore, (2) should be believed over (1)

When trying to decide between idealism and realism, of course anything is possible. Everything could be real, exactly (or nearly) as it seems, we could be inside a futuristic computer simulation or matrix-like universe, we could all be dreaming, or the subjective idealists could be right - everything we see outside ourselves is "mind dependent" and only exists because it is there to be perceived. I could live in a universe where only I exist and am inventing all of you, or the entire world could have been created last Thursday. Yes, anything is possible, and unfortunately, apriori logic cannot be used to disprove any of them (as Hume said, discussed elsewhere in this series). But we should consider the difference between what is possible and what is probable. Although the dream scenario may be possible, is it likely? Probably not. There is no compelling reason, and no evidence for, dis-believing in the real world. Although many possibilities exist that would account for our experiences, only one is probable. Only one, the realist view, explains the consistency of our experiences, explains that everyone has essentially the same experience of the world (within the error bars of perceptual and psychological differences), and requires no miracles or superfluous inventions. The others are ad hoc, and exist merely to fit the data but are otherwise incapable of offering any explanations, predictions, or descriptions of the world. Given that, the most plausible and rational explanation for our experiences in life is that what we see outside ourselves is actually there. Although the other options are technically within the realm of possibility, it would be perverse, contrary, and obstinate to prefer one of those alternative explanations.

5.1.2.6.1 Russell and Reality

Bertrand Russell addressed the issue of matter and the external world. He sets out to decide whether we can be sure that matter (i.e., the external world) exists or if we must admit that matter is something imagined, only as real as a dream might be said to be real. Since we identify matter with physical objects, the criterion for our certainty in external reality is the independent existence of physical objects. The goal now is to establish what many philosophers suspect, that objects exists independent of our perception of them, that if we turn away from them, they continue to exist. Although we may doubt the physical existence of an object, such as a table, "we are not doubting the sense-data, which made us think there was a table," the immediate experiences of sensation. In this sense he was like Descartes, who had certainty only in his own thoughts.

If the table is real, then our confidence in our senses has been well-placed, and we might be said to have reasonably inferred reality from its appearance. If we find that the table is not real, then the "whole outer world is a dream." One hypothesis affirms our common-sense view of reality, and the other holds that "we alone exist" and nothing we experience is real in our ordinary sense. Russell contends that it cannot be proved that we are not dreaming "alone in a desert," but also argues that there is no reason for supposing that this is the case.

It is always a logical possibility that we are deceived about the true nature of reality and that it is hidden from us. It is possible because "no logical absurdity results from the hypothesis that the world consists of myself and my thoughts and feelings and sensations." However, Russell's argument is that though there may be no way to disprove this "uncomfortable" possibility, there is no reason in support of it either. What is simpler and more plausible is the hypothesis that independent physical objects exist "whose action on us causes our sensations." The advantage of this hypothesis is in its simplicity. It explains the phenomena of our lives with the least resort to invention. It is the most parsimonious, though it cannot be proved deductively.

My opinion is that, at least recently, the modern emphasis on deductive proof is the popularity of television crime shows, Mr Spock from Star Trek, and the popular notion that Sherlock Holmes was a master of deduction. In fact, this is elevating the exercise of deductive logic to a prominence that it really should not have. In life, in science, and even in Sherlock Holmes novels, it is not deduction that solves the crime but induction, also known as inference. Specifically, the technique he used was called abduction, or "inference to the best explanation". Deductive reasoning is applicable primarily in highly controlled scenarios such as in proving mathematical theorems, logic, and in applied areas of technology such as software and circuit design - where the conclusion is completely contained in the premises. In life, we usually generalize from the specific to the general through inductive methods.

In fact, inference to the best explanation (eliminating unlikely explanations, leaving ourselves with the single "best" explanation) is used in everyday life far more frequently than either deduction or standard induction. It is how we draw conclusions from partial information. It is how we evaluate social interactions, judge intents of others, and understand potentially ambiguous statements. It is the primary tool of medicine, science, and all other forms of research and discovery.

In making these types of inferences, we infer from the fact that a certain hypothesis would explain the evidence, to the truth of that hypothesis. In general, there will be several hypotheses that could potentially explain the evidence, so we systematically consider each one and reject all the least likely ones, leaving one remaining. In this manner, we are able to infer from the premise that a given hypothesis would provide a "better" explanation for the evidence than would any other hypothesis, to the conclusion that the given hypothesis is true. Accepting one of the less probable ones would simply be perverse. For Russell, and for most people, the separate existence of a physical world is the best explanation for our experiences, beating out solipsism, Last Thursdayism, Matrix ("brain in a vat") theories, and devious/malicious/deceiving gods. It is the only one consistent with the "No Miracles Argument", in that it is the only explanation that does not require a miracle for it to be the right theory. Now, there is no particular law that says miracles should be avoided in our theories of reality, but miracle-based explanations are highly ad-hoc, and experience has shown ad-hoc explanations (explanations developed merely to cover the facts, and nothing more) are usually wrong.