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The Art of Living

Cicero & the Value of Skepticism

Massimo Pigliucci is not skeptical about skepticism itself.

The word ‘skepticism’ has often had a bad reputation. My dictionary tells me that a skeptic is “one who instinctively or habitually doubts, questions, or disagrees with assertions or generally accepted conclusions.” Yet the original meaning of the word, from the Greek skeptikos, is something along the lines of ‘someone who inquires and reflects’ on things. Can skepticism be a philosophy of life rather than just an epistemic attitude?

In my recent book, How to Be a (Happy) Skeptic: The Power of Doubt in a Meaningful Life, I examine this question by considering the life and philosophy of Marcus Tullius Cicero (106-43 BCE), the orator, statesman, and philosopher who lived at the end of the Roman Republic and who was both a friend and an enemy of Julius Caesar (not at the same time!).

Cicero had an outsized impact in his own lifetime, during his desperate but ultimately unsuccessful fight to save the Roman Republic from becoming an Empire. He subsequently influenced imperial authors from Virgil to Seneca. During the Middle Ages he was read by Boethius and Augustine, and his conception of natural law deeply influenced the Christian tradition of it. The Renaissance itself is sometimes said to have started when Petrarch rediscovered Cicero’s letters. Cicero was also greatly admired by Enlightenment authors from Montesquieu to Locke. His ideas on mixed government, natural rights, and civic virtue appear throughout the Federalist Papers and the U.S. Declaration of Independence. His concept of res publica (‘the public thing’) helped shape modern democratic theory. My project however, was to investigate how Cicero’s skepticism informed, and was in turn influenced by, his life experiences, in both the private and public realms.

Cicero was a student of the skeptical tradition within Plato’s Academy. This means he embraced the skeptical philosophy of Carneades of Cyrene and Philo of Larissa. The basic idea is that human knowledge is rooted in two ultimate sources, reason and sense experience, but we know they’re both fallible – which means that knowledge itself must be considered tentative. We therefore assess claims to knowledge on the basis of what Carneades called pithanon (likelihood). Cicero brilliantly translated this term into Latin as probabilis, from which we get the modern English ‘probability’.

If you apply the skeptical concept to everything, you get the refreshing notion that you can provisionally endorse a given ethical, political, scientific, or personal opinion yet reserve the right to change your mind about it, should new arguments or evidence convince you to do so. As Cicero put it in his Tusculan Disputations: “We should not be too confident in our belief of anything.”

This doesn’t mean that skeptics are paralyzed, unable to act. In fact, they devised a semi-quantitative scheme for assessing the reliability of ‘impressions’ – the opinions we naturally form about this or that idea or experience. An impression may be, in increasing order of strength, ‘apparently true’, ‘convincingly true’, ‘undiverted’, or ‘thoroughly explored’. Let me give you some examples.

Apparently true: You glance at your coffee mug on the desk and form the impression it is still half full, as it looks that way to you. The impression is plausible, so you don’t get up to refill it – but you’re not going to bet much on the idea, and you’re ready to act otherwise if it turns out you’re mistaken.

Convincingly true: You hear what sounds like your name called across a noisy train station. The impression is not just that someone was called, but that it was you, since the sound fitted the shape of your name. More than mere appearance, the experience compels assent. Still, you might be wrong.

Undiverted by other impressions: You’re about to sit down in what you believe is your assigned seat on the plane. The row number matches your boarding pass, the seat letter is correct, and the passenger in the adjacent seat isn’t challenging you. Nothing in the surroundings undercuts the impression. It coheres with all the available evidence.

Thoroughly explored: A physician suspects a patient has a particular condition. She has reviewed the symptoms carefully, ordered confirmatory tests, ruled out competing diagnoses, and consulted a colleague. Every line of inquiry she can reasonably pursue points in the same direction. She acts on this impression with the highest degree of justified confidence, while still falling short of absolute certainty.

I said this scheme was ‘semi-quantitative’ because we can assign tentative probabilities to each of the four conditions: say, respectively: apparently true: just greater than 50%; convincingly true: 60-80%; undiverted: around 90%; and thoroughly explored: close to or even above 95% certainty. This skeptical attitude, then, is that of a Bayesian updater: we keep revising the likelihood for the impression to be conveying truth as new information comes in, increasing or decreasing it according to what we learn. The more important something is, the more we want to be confident that we’re correct about it, which means that we need to further our inquiries, as any good skeptic would do.

When you have a moment, list some beliefs you currently hold, assess them using the four criteria above, and ask yourself what sort of new evidence would alter your probability estimates. Get into the habit of doing this, and you’ll be on your way to becoming a true skeptic. Of that I’m almost certain.

Massimo Pigliucci is the K.D. Irani Professor of Philosophy at the City College of New York. His books include How to Be a Stoic: Using Ancient Philosophy to Live a Modern Life (Basic Books) and How to Be a (Happy) Skeptic (Penguin). More by him at figsinwintertime.substack.com.