Skepticism is a hard-headed philosophy. Its hallmarks are intellectual caution, systematic doubt, and rigorous standards for evidence. This makes it easy for the skeptic to claim the intellectual high ground. When the atheist Bertrand Russell was asked what he would say if he were to die and find out that there is a God, his response was, “Not enough evidence God! Not enough evidence!”
Let’s table the issue of evidence for now and directly challenge the skepticism, which suffers from two main problems. The first is that skepticism is self-refuting. The second problem is that skepticism leads to absurd conclusions that no one believes, including the skeptic.
Skepticism is Self-Refuting
Here is a famous quote by William K Clifford:
“It is wrong always, everywhere, and for anyone, to believe anything upon insufficient evidence.”
But where does Clifford get the evidence to back up this assertion? Its doubtful that you could even devise a scientific experiment to put it to the test (and if you could, it would probably falsify Clifford’s hypothesis - see below). Clifford believes his assertion without evidence, so by his own standard, he must reject his assertion as wrong.
Here is A.J. Ayer’s statement of logical positivism’s verification theory of meaning:
We say that a sentence is factually significant to any given person, if and only if, he [or she] knows how to verify the proposition which it purports to express—that is, if [she or] he knows what observations would lead him [or her], under certain conditions, to accept the proposition as being true, or reject it as being false.
But if this verification principle is true, then logical positivists need to devise some sort of scientific test that will confirm or reject this principle. But there is no such test. Thus logical positivism is self-refuting.
Here is a famous quote ‘An Inquiry Concerning Human Understanding’ by David Hume:
If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, Does it contain any abstract reasoning concerning quantity or number? No. Does it contain any experimental reasoning, concerning matter of fact and existence? No. Commit it then to flames: for it can contain nothing but sophistry and illusion.
Is Hume’s ‘An Inquiry Concerning Human Understanding’ contain abstract reasoning concerning quantity and number (i.e. is it a math book)? No. Does it contain any experimental reasoning; concerning matter of fact and existence (i.e. is it a science book)? No. Then Hume’s conclusion about his own philosophy is that it should be committed to flames: for it contains nothing but sophistry and illusion.
The 20th century philosophy Ludwig Wittgenstein echoed Hume’s in his book ‘Tractatus’ but Wittgenstein was more aware of the problems his skepticism created. He wanted Hume’s advice to be taken literally: burn his book and then never think about God or other metaphysical questions again. But ignoring a problem will not make it go away: in both cases their philosophy is self-refuting. Wittgenstein ultimately rejected his original position.
Skepticism Leads to Absurd Conclusions
More sophisticated skeptical arguments can avoid being self-refuting. But there is a second fatal flaw for the genre, which is that skeptical arguments lead to absurd conclusions. These conclusions are often the strange “if a tree falls in the woods and there is no one there to hear it, does it make a sound” fodder that make most people (rightly) skeptical of philosophy itself.
Most of these examples are lifted directly from the philosophy of the patron saint of skepticism, David Hume.
- The Demon. Also known as the “brain in a vat.” This is probably the most famous problem in all of philosophy for the past several hundred years. Imagine that for your whole life everything you ever saw, heard, touched, tasted and smelled was actually the illusion of an evil demon. To put it in modern terms, suppose your whole life is a clever virtual reality illusion, and that in the real world you are nothing but a “brain in a vat.”
The brightest minds in philosophy have spent hundreds of years trying to refute this idea and they have all failed, although a few mavericks would beg to differ.
- External objects. If you think about it, we can never get “outside” of our senses. Sure you can see a tree, but all we can rationally conclude is that there is the perception of green (the leaves) and brown (the trunk). If touch the tree we can conclude that there is the sensation of a rough hard surface. If the wind blows we get the perpection of rustling leaves. But this does not allow us to conclude that there is a tree “behind” all these sense-perceptions. We can only conclude that there are a cluster of sense perceptions. The common man believes in trees, but the wise skeptic knows that all there is only the perception of trees.
- Enduring objects. It could be the case that objects wink out of existence when no one is looking at them (through video or otherwise).
- Other Minds. It could be the case that you are the only person in the world who is self-conscious. Everyone else is the living equivalent of a cleverly programmed robot. They may claim to be self-concscious if you ask them, but only because that is what their programming has them do. You are a lonely person, the only self-aware being in the universe.
Here is another way to reach the same conclusion. From our examples above, it is clear that all that exists are sense-perceptions. And if you think about it, those sense perceptions are simply mental states inside your own head. Other people are merely part of your mental states (perhaps put there by the evil demon?). But something that is just a part of one of your mental states cannot be self-conscious.
- The Past. We think that the past happened. But as Bertrand Russell points out, it could be the case that the universe sprang into existence five minutes ago in its current state. We have memories of a past that never happened, and partially digested food from meals that we never ate in our bellies.
- Self. We think of ourselves as one continuous person that persists through time. But careful thought reveals that this is an illusion. All we can know is our current mental state. We may think that we know other mental states - for example, you may recall several different memories. But that recollection is but a single mental state. In other words, some mental states have illusions of there being many mental states, all held by the same person. But since there is no way to prove that these other mental states occured, the skeptic claims, we are not justified in thinking that they ever happened. Thus we cannot conclude that there is an enduring self. There is only the present mental state.
- Causality. We think that ‘A’ causes ‘B’ is reasonable, but careful thought reveals that this isn’t. We can repeatedly see event ‘A’ followed by event ‘B’ but we never see ‘the cause.’ We can only rationally conclude that ‘B’ follows ‘A.’ Thus there are not rational grounds upon which to believe in causality.
Needless to say, these are all absurd conclusions. But it is also clear that it is almost impossible to mount even a feeble defense of common sense. In some cases Occam’s Razor may help, for example, it is simpler to assume that there is only one type of human being than two types. And since you are self-conscious, then other people must also be self-conscious. But that falls well short of direct evidence, it remains a plausible theory that needs to be tested. And in other cases, Occam’s Razor works against us: it is simpler to conclude that the universe consists of just yourself and the Demon.
The real lesson is that our belief structures require a foundation - beliefs that are simply accepted rather than based on evidence of other beliefs. Alvin Plantinga has created a rigorous theory of knowledge in which all of the common sense positions are accepted as part of the foundation, including the existence of God. The radical conclusion: belief in God simply does not need evidence (although plenty of evidence exists).
