The title of this blog is drawn from one of my favorite philosophical arguments: G. E. Moore’s Proof of an External World. Moore gave the following proof of the existence of things outside our minds:
- Here’s one hand (waves his hand).
- Here’s another (waves other hand).
- Therefore, there are external objects.
Moore’s proof may sound like he was trying to be a smartass, but he was entirely serious. He believed that this argument proved that there were things outside our own minds that we could have knowledge of. The hand gestures are a key part of the proof. Moore was proving that a certain sort of thing existed (external objects) by providing examples of them.
For centuries, philosophers had been trying to provide a rational argument for the existence of the external world. They didn’t think that simply giving examples would be enough. However, this sort of proof is accepted all the time. If someone claims to have the newest iGadget before it’s out on the market, they can prove it by showing it to you. Most people don’t believe that the Loch Ness monster exists, but if we actually dragged one out of the loch, that would be enough to end the debate. Ordinary standards of evidence legitimize the sort of proof Moore offers.
So why did philosophers wonder for so long if they could know that there are tables and chairs, and waving hands out there in the world? The historical story is too long to go into in detail, but ultimately the reason is that they believed that before we could trust our senses, we needed reasons to believe that they could be relied upon, and that the only way we could offer such assurance was by using reason.
Part of what Moore was doing with his proof was arguing that this is the wrong way to look at evidence. When we care about the truth, we accept the evidence of our senses as a good reason to believe things. We take eyewitness testimony seriously, and would laugh at someone who still claimed something didn’t exist after seeing it with his own eyes. We don’t do this because we haven’t taken enough philosophy to learn that real evidence is philosophical evidence. We do it because standards of evidence already exist in ordinary life, and they correspond, more or less, to the actual strength of the reasons they provide.
Philosophy should be engaged in the rational pursuit of truth. But not all rationality is a matter of philosophical arguments. Good reasons for belief can come in a variety of forms. In fact, as a matter of logical necessity, arguments are one of the worst sources of evidence we can have. Arguments depend upon the strength of their premises for the evidential support they offer. But that means that we must antecedently have good reason to accept those premises on which they depend. Barring an infinite set of arguments behind them, these premises must depend on ways of knowing that are legitimate independently of philosophical reasoning. It is only because we have so many other ways of knowing that we can engage in philosophical reasoning to learn more about the world. The view endorsed by people like Moore and Thomas Reid that philosophy is dependent on common sense isn’t some arbitrary proclamation. Philosophy should grow out of common sense because philosophy is entirely dependent on it. Arguments, reasoning, and debate can take us beyond where we began, but they can’t fundamentally change or overturn our foundational view of things without losing its own credibility.
Moore’s proof helps remind us of this. It helps us see the place of reasoning in understanding the world, and helps keep us from becoming so enamored of our clever arguments and skillful reasoning that we are willing to ignore what we have always known, and have always had far better reason to believe.