reported, “Professor, every time I say anything new in our class, your little boy blurts out, ‘Prove it!’ Could you please have a talk with him and explain that no one can prove everything?” My friend had to laugh and go have a chat with his demanding young rationalist. As the philosopher John Locke concluded from his own research into the nature of proof, “He that, in the ordinary affairs of life, would admit of nothing but direct plain demonstration would be sure of nothing in this world but of perishing quickly.” Solid proof, or in Locke’s language, demonstration in life is rare and so is not ordinarily required.
It seems clearly excessive to think that no belief is rational to hold unless the believer is in possession of some decisive and compelling proof that it’s true. You have beliefs about the galaxy, nuclear energy, your computer, and even your own body that you can’t prove in any decisive sense. You can most often produce some bit of evidence, or the reported testimony of some expert, or at least a vague memory of having once had either evidence or testimony for the truth of what you believe, but you are rarely in possession of a knock-down, incontrovertible proof. Life just doesn’t work like that.
As a result of this realization, some philosophers have suggested that perhaps it is excessive to require proof for rationality, but it may indeed be necessary to have at least sufficient evidence in order to be justified in believing anything.
On this philosophy, widely known as evidentialism, it is irrational ever to believe anything without sufficient evidence that it’s true. Hearsay is not enough, sheer faith is never alone to be trusted, and an unsupported intuition is not admissible at all. Hard evidence or nothing is the demand. But this may itself not be a reasonable demand. Rational belief may not even always dependent on evidence. And that’s a surprise to many people. It’s a matter that Chapter 5 in this book explores.
Philosophy involves an exploration of the biggest questions about human life and its context, as well as a determined search to find answers. Any possible answer or belief on these big issues must be assessed carefully for its truth, and that most often means examining any evidence or argument or any other serious consideration we can find that might indicate its truth. And this requires logical thinking. Logic is vital. You can’t just go with a hunch or a feeling, but have to test ideas logically, first to understand them fully, and then to evaluate them well. It will take you on one of the most unusual intellectual journeys of your life to answer the biggest, deepest questions about evidence and rationality and what logical scrutiny can tell us about them, a journey to be undertaken in the next two chapters. So, if you’re up to it, buckle up your mental seat belt, keep reading, and prepare for the philosophical ride of your life.
Chapter 5
The Challenge of Skepticism
IN THIS CHAPTER
Doubt is the vestibule which all must pass, before they can enter into the temple of truth.
— Charles Caleb Colton (1825)
We live in a culture awash in information. We’re drowning in data each day. The media trumpet that, with the advent of modern communications and advanced technology, human knowledge is expanding geometrically faster than at any other period in history. Some say knowledge at least doubles every four years now. Others claim the growth of what we know is even faster.
But the question is whether we really know all that we think we know and whether all this new information really amounts to knowledge or not. You can easily come to wonder if it’s precisely knowledge that is expanding, or just belief, or perhaps mere opinion. The constant and rapid flow of apparent information into our lives may lull us into thinking we have increasingly more knowledge, when actually we may be gaining nothing of the kind. We may not know even a fraction of what we think we know. In this chapter, we look at the most ancient challenge to our claim to have knowledge, and we actually discover from it some deep and important insights we all need.
Since the ancient world, philosophers have cautioned about humankind’s natural tendency to claim knowledge where knowledge, in fact, may not exist. The ancient philosophy of skepticism can help you to understand more deeply what exactly knowledge is, and where it comes from, as well as to answer the open question philosophers have often asked of whether evidence is always required for rational belief, and thus for knowledge.
In this chapter, you will see how the most basic form of skeptical inquiry can give a fresh perspective on the foundations of all human knowledge. You’ll be introduced to some fundamental questions you’ve likely never asked, and in the process of trying to answer them, you’ll discover an overlooked principle of rationality. This just may be the most philosophically challenging chapter in the whole book, but if you can grasp its reasoning and its implications, you’ll see all the other issues of philosophy in a new way. The questions that are raised by skepticism can put everything in a new light, and can inspire you with a needed humility and deeper perspective concerning all claims to knowledge.
Introducing the Ancient Art of Doubt
The words skeptic and skepticism come from an ancient Greek verb that meant “to inquire.” Etymologically, then, a skeptic is an inquirer. This should form an important background insight for your understanding of skeptical doubt. Skepticism at its best is not a matter of denial, but of inquiring, seeking, questioning doubt. As long ago as Homer’s Odyssey, we find the striking exclamation: “How prone to doubt, how cautious are the wise!” Wisdom often begins in skeptical questioning, in productive doubt seeking understanding.
The first great skeptical philosopher in the ancient world was Pyrrho of Elis (c. 310–270 BCE). It is said of him that, after traveling with Alexander the Great as a court philosopher, he returned home to teach great crowds of admirers and wisdom seekers. Pyrrho was known for presenting philosophy as a way of life that aims at a calmness of the spirit and happiness of the heart.
This philosopher believed you should always be quick to question and slow to believe. He seemed to think that people too easily can become convinced of things that trouble their minds and disturb their souls. So he practiced and preached withholding judgment, or assent, as much as possible.
Some stories from his time portray Pyrrho as perhaps far too calm, and even indifferent about real dangers in his daily environment. Apparently, his friends were constantly saving his life, pulling him from the paths of speeding carts, from the edges of cliffs, and away from other dangers. Commentators ascribe this to his skeptical disinclination to trust his senses, and thus to a philosophical reluctance to believe anything that appeared to be going on around him. But it’s easy to doubt this, appropriately enough. In graduate school, my best friend and I frequently saved each other’s lives, alternately pulling each other back from the paths of oncoming cars as we walked the streets of New Haven, Connecticut, deep in thought. Our apparent indifference to the dangers
