Can We Ever Be Sure of Anything? Latin America’s Skeptical Heart
A Classroom in Campinas: Why Ancient Doubt Still Matters
In 1986, a group of philosophers gathered in Campinas, Brazil. They came to talk about a set of ideas so old that they were first written down in ancient Greece. Those ideas asked a terrifying question: what if you could never be completely sure about anything? The star of the event was a Brazilian philosopher named Oswaldo Porchat Pereira (1933–2017). He didn’t just study this ancient form of doubt — he called himself a modern follower of it. He was a neo-Pyrrhonian.
Skepticism is the view that we lack knowledge, or that we should be careful about claiming it. But Porchat’s kind of skepticism went deeper. It came from a school called Pyrrhonism, named after Pyrrho of Elis (c. 360–270 BCE), whose teachings were written down centuries later by a doctor named Sextus Empiricus. Pyrrhonists didn’t just say “I doubt this or that.” They aimed for suspension of judgment about almost everything — including whether things really are the way they appear. Instead of forming beliefs, they tried to live by simply going along with how things seem, without deciding that those appearances match reality.
Porchat’s Argentine friend Ezequiel de Olaso (1932–1996) also spent his career studying skepticism, from Sextus to modern figures like David Hume and Gottfried Leibniz. But de Olaso didn’t join the skeptics. He thought their arguments were powerful, but he kept a critical distance. The two men, one from Brazil and one from Argentina, helped make Latin America one of the world’s most lively homes for arguments about whether any of our beliefs can survive deep questioning.
Can You Live Without Beliefs? The Neo-Pyrrhonian Challenge
Porchat’s big claim was that you can live a full human life while suspending judgment about nearly everything. In his neo-Pyrrhonian picture, you don’t need to believe that the world is a certain way. You just follow what appears to you. If you feel hungry, you eat — not because you believe the food exists or that eating will stop the hunger, but simply because it appears to you that eating is the thing to do. You act without committing to beliefs.
Critics, including de Olaso and later philosophers, pushed back hard. One objection was that action requires belief. If you genuinely don’t believe the car in front of you is real, why would you step out of its way? The skeptic responds: you step aside because the appearance of danger moves you, not because you’ve formed a belief about danger. But many philosophers find this reply too thin. Juan Comesaña (b. 1972), an Argentine philosopher now working in the United States, examined whether modern theories of knowledge could help Pyrrhonists escape this “inactivity” problem. His verdict was that the skepticism still can’t explain how we manage to get through the day.
The ancient Pyrrhonists themselves had a famous set of arguments to produce suspension of judgment: the Five Modes of Agrippa. One mode points out that every claim can be challenged with a reason, and that reason with another reason — an infinite chain. Another shows that people disagree endlessly. A third says that if you try to stop the chain, you just assume something without proof. Together they create a trilemma: your reasoning goes on forever, circles back on itself, or stops at an unproven foundation. To a Pyrrhonist, none of those is acceptable, so you should suspend judgment.
Otávio Bueno (b. 1970), a Brazilian philosopher trained by Porchat’s students, argued that the Pyrrhonist isn’t actually committed to any strong theory of knowledge. The arguments are dialectical — they’re just tools to show opponents that their own standards lead to trouble. The skeptic doesn’t have to prove that we can’t know anything; she just has to show that, by your own rules, you can’t either. This keeps the skeptical challenge alive without making it a fixed doctrine.
Fighting Back with Logic: Reliabilism and Safety
As Latin American philosophy grew more connected with the analytic tradition in the United States and Europe, a younger generation started attacking the challenge of skepticism with precise logical tools. Instead of just interpreting ancient texts, they built theories of knowledge and justification and tested them against the skeptics.
One of the most influential ideas they worked with is reliabilism — the view that a belief counts as knowledge if it is true and was produced by a reliable process, one that tends to yield true beliefs. You don’t need to be able to explain why the process is reliable; it just has to work reliably, like your vision in good light. Eleonora Cresto (b. 1971), an Argentine epistemologist, explored whether reliabilism could answer skepticism. She found some standard versions wanting, but also tried to craft a stronger reliabilist reply of her own.
Comesaña offered an original twist: evidentialist reliabilism. It combines the reliabilist’s focus on reliable mechanisms with the evidentialist’s insistence that you need evidence for your beliefs. He also challenged a popular idea called the safety condition. Safety says that if you know something, then in nearly all similar situations, you wouldn’t believe it falsely. Comesaña argued that safety, as defined by some big-name epistemologists, fails — you can have knowledge even when your belief isn’t perfectly safe, because reliability only needs to hold in the actual world, not across all nearby possible worlds.
These thinkers didn’t just repeat what their Anglophone colleagues said. They entered the same debates and contributed new arguments and counterexamples, making the Latin American conversation part of the global one.
The Mathematicians Who Taught Computers to Change Their Minds
While the skeptics debated whether we can know anything at all, a completely different group of Argentine researchers asked a more practical question: how should a rational mind (human or machine) update its beliefs when it learns something new? Their answer became one of the most successful ideas in modern formal epistemology — the use of logic and probability to study knowledge.
The central figure was Carlos Alchourrón (1931–1996), a philosopher and lawyer in Buenos Aires. Together with Peter Gärdenfors and David Makinson, he published a 1985 article that gave birth to the AGM theory of belief change. The theory describes three operations on a set of beliefs. Expansion simply adds a new belief that doesn’t conflict with anything you already think. Contraction removes a belief. Revision is the trickiest: you add a new belief and remove others just enough so the whole set stays consistent.
The AGM trio proposed a list of postulates — rules that any sensible belief-changing system should obey. For example, when you revise your beliefs, you should give up as little as possible of what you already held. The theory doesn’t tell you which specific beliefs to drop (that depends on what you consider most important), but it spells out the structure any rational update must have. Since then, hundreds of papers have refined the AGM framework, and it has been used to design artificial intelligence systems that adjust their knowledge bases without breaking.
Horacio Arló-Costa (1956–2011), a Uruguayan student of Alchourrón, became a leading figure in formal epistemology worldwide, extending the AGM ideas into Bayesian reasoning and decision theory. Brazilian computer scientists like Odinaldo Rodrigues (b. 1968) and Renata Wassermann (b. 1971) applied belief-change logic to non-classical logics and software engineering. The result is a Latin American legacy that isn’t just about interpreting old books — it’s running inside the software you use.
Why Latin America’s Mix of History and Math Still Matters
So why should a twelve-year-old today care about a debate between Brazilian skeptics and Argentine logicians? Because the questions they wrestle with are yours too. Every time you change your mind about a friend’s story, decide which news report to trust, or watch your phone’s map recalculate a route, you’re right in the middle of the problems they explored.
The skeptics remind us that much of what we “know” rests on assumptions we never bother to check. The next time you’re absolutely sure about something — that a video game world is unfair, that a sibling is lying — ask yourself: could a really clever skeptic force you to keep asking “why?” until you had to admit you can’t give a final reason? That’s the Agrippan trilemma in your own head.
The AGM logicians, on the other hand, show that changing your mind can be done carefully, with rules that keep your whole set of beliefs from collapsing into contradiction. When you learn something surprising, you don’t just dump everything you ever believed — you tweak the system. The mathematicians gave us a language for talking about that tweaking.
Latin America’s philosophical story isn’t about one single doctrine. It’s about a culture that brings together ancient texts and cutting-edge logic, profound doubt and precise calculation. And it’s still growing. More and more researchers are connecting the old skeptical arguments with the newest tools from computer science, forming a community that may soon have its own unmistakable voice. In the meantime, their debates belong to anyone who has ever wondered: “How do I really know?”
Think about it
- If you couldn’t be absolutely sure of anything at all, would you still be able to live a normal day — eat breakfast, go to school, talk to friends? What might change and what might stay the same?
- Imagine your phone learns a new fact that contradicts something else it “knows.” How should it decide what to keep and what to throw away? Would your rules work for a human too?
- Some neo-Pyrrhonians claimed we can live without forming any beliefs. Do you think it’s possible to walk down a busy street while genuinely believing nothing about the street, the cars, or yourself? Why or why not?
