Socrates, Plato’s mentor and the chief protagonist of nearly all of Plato’s dialogues, frequently insisted that he knew nothing.

Plato’s Theaetetus, then, is a book about the nature of knowledge, built by a writer who distrusted writing, conveying the words of a man who maintained he had no knowledge to offer.

And yet, as Professor Richard Polt puts it, “the entire subsequent history of philosophy is a footnote not just to Plato in general, but to these very pages.”

In Plato’s Theaetetus: An Inquiry into Knowledge, a new five-part series from Ergo, Polt presents a course designed as an introduction to the dialogue, to Plato, and to philosophy.

Beginning with the question “What is knowledge?”, the series follows an argument among a small cast of characters. At the center is Socrates, seventy years old in this dialogue, a man who calls himself a midwife, helping others give birth to ideas he claims he could never produce himself. Opposite him stands Theaetetus, a young mathematician praised by his own teacher as both sharply intelligent and unusually steady. That teacher is Theodorus, a more conventional instructor who hands over answers rather than drawing them out of his students.

The pressure is on young Theaetetus for much of the dialogue, with Socrates pushing the student past limited examples of what knowledge might be until he arrives at the claim: “knowledge is perception.” That assertion opens onto some of the largest ideas in Greek philosophy: Protagoras’s teaching that “man is the measure of all things,” and Heraclitus’s conviction that everything is in constant flux. Polt follows the two threads as they tangle together into a picture of reality with no fixed things in it at all. By the later lectures, perception alone can no longer carry the argument, and the conversation turns from what the senses report to what the mind does with it: judgment.

This seemingly firmer ground quickly shifts again, as befits a dialogue run by Socrates. “You should not necessarily believe what he says or assume that his arguments are sound,” Polt warns his audience early in the series. “He is ironic, he is playful, he is deliberately unsettling people’s assumptions.”

Polt explains that philosophy should seek to throw familiarity into question. “Philosophy is never about new information,” he says. It is “about very familiar things, like knowledge. Everyone is familiar with knowledge, and yet we cannot seem to grasp it, define it, or explain exactly what it is.” In Socratic fashion, Polt encourages his audience to leave with new questions, and, in the face of uncertainty, to begin dialogues of their own.

All five lectures can be viewed on Ergo or on YouTube.

Richard Polt is a Professor of Philosophy at Xavier University. He holds a B.A. in philosophy from the University of California at Berkeley and a Ph.D. from the Committee on Social Thought at the University of Chicago. His interests include German and Greek philosophy, and he has taught courses on Heidegger, memory, history, technology, and African-American philosophy.

Polt’s publications include Heidegger: An Introduction, The Emergency of Being: On Heidegger’s Contributions to Philosophy, and Time and Trauma: Thinking Through Heidegger in the Thirties. He has also edited or co-edited volumes including A Companion to Heidegger’s Introduction to Metaphysics, Heidegger’s Being and Time: Critical Essays, After Heidegger?, and The Task of Philosophy in the Anthropocene.

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Today, computers can chart optimal driving directions across an entire continent, answer nearly any question put to them, hold a fluent conversation, and write working code, all within seconds. These achievements raise a natural question: is there anything computers cannot do?

Professor Tim Roughgarden takes up this question directly in Computation as a Universal and Fundamental Concept, a new five-part series from Ergo. What does it mean to understand computation as a law of nature? How far have we really progressed beyond the concept of a computer proposed ninety years ago by Turing? In an age of quantum computing and generative AI, are we capable of progressing further?

Across the five lectures, Roughgarden illustrates that computer science has always simultaneously pulled in two directions: toward proving what computers can do, and toward proving what they cannot.

One direction is the search for upper bounds, proof that computers can do more than expected. Anatoly Karatsuba disproved his professor’s confident conjecture that the method for multiplication we all learned in grade school could not be improved upon, developing a powerful new algorithm in a single week.

Edsger Dijkstra found the shortcut still running your phone’s driving directions.

George Dantzig built an entire mathematics of optimization, linear programming, to solve a military logistics problem. John von Neumann, shown the result, spotted its hidden connection to game theory.

The other direction is the search for lower bounds, proof that computers cannot do something no matter how the technology improves. This is Turing’s legacy, with the halting problem as the most famous example.

By the early 1970s, the search for upper bounds and the search for lower bounds had converged on the same question: P versus NP. P versus NP asks whether every problem where a proposed solution is easy to check once someone hands it to you is solvable by an algorithmic shortcut.

The stakes are enormous specifically because so many different problems turn out to be, in a precise mathematical sense, the same problem. Sudoku, the Traveling Salesperson Problem, and thousands of others across logistics, scheduling, and biology are all versions of one another: solve any single one of them quickly, and a fast solution to all the rest follows automatically.

Having brought us this far, Roughgarden leaves us with two possible worlds. If P equals NP, all of those thousands of problems fall to fast algorithms at once, and what is possible in science and industry expands overnight. If P does not equal NP, all of them remain permanently out of reach, and the shortcuts that have worked so well elsewhere in computer science simply do not apply here.

Nobody yet knows which world we are in. As we approach quantum computing and develop better AI, Roughgarden again brings us back to Turing and his machine. Some of the boundaries Turing drew in 1936 remain exactly where he left them, untouched by ninety years of progress. Others turn out to be more fragile than expected, at least once quantum mechanics enters the picture. Roughgarden’s series lays out exactly which limits are which, and shows why a technology capable of unsettling one boundary can leave a neighboring one completely intact.

All five lectures can be viewed on Ergo or on YouTube.

Tim Roughgarden is a Professor in the School of Mathematics at the Institute for Advanced Study. He previously spent seven years on the computer science faculty at Columbia and 15 years at Stanford. His main interests are in the connections between computer science and economics, and in the design, analysis, and limits of algorithms.

He is the author of Twenty Lectures on Algorithmic Game Theory, Beyond the Worst-Case Analysis of Algorithms, and the Algorithms Illuminated series, as well as numerous research articles. His work has been recognized with several major awards in theoretical computer science, including the ACM Grace Murray Hopper Award and the Gödel Prize.

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Throughout the Middle Ages, the universe came with what Braver calls “an owner’s manual for human life”: the Bible. Everything a human had to know about being a human, and everything they needed to know about the cosmos, was contained within that book. Trying to deviate from the ultimate authority and somehow “reason out” the big questions of life was the medieval equivalent of ignoring Google Maps in an unfamiliar city, and trying to reason your way to the hotel by staring at the street layout.

Renés Descartes put himself in just such a position. On a snowy evening in 1619, he set out to abandon all authority, and rebuild the entirety of human knowledge from scratch, without appeal to scripture, teachers, or tradition. Braver says Descartes was motivated by what he saw as the shortcomings of his era. The education of his day could not cure disease, build new machines, or do much of anything else to improve human life. He believed a properly rebuilt science could finally deliver those benefits.

Descartes’ project succeeded beyond anything he could have imagined. And as the scientific revolution continued on its course, Braver illustrates how philosophy worked to keep pace. Hume showed that humanity’s newfound confidence in reason rested more on assumption than on proof, and Kant showed that the mind supplies the very structure it later claims to discover, securing science while closing the door on the true nature of reality. As Braver puts it, “Kant giveth and Kant taketh away.”

By the time Nietzsche comes on the scene, three centuries of scientific progress have come at the cost of a deep crisis of meaning. Science has replaced the Bible as our guide to the world, and it does not come with the built-in sense of purpose and cosmic significance the Bible once offered. Nietzsche is the philosopher willing to say so out loud, in the phrase that now precedes him everywhere: “God is dead.” Braver encourages us to asks what we can do with such a realization. How can we soldier forward toward the undrawn parts of the map?

All seven lectures available on Ergo or on YouTube.

Lee Braver is a Courtesy Professor of Philosophy at the University of South Florida, where he was a Professor of Philosophy from 2012-2025. His main interests are in continental philosophy (especially Heidegger and Foucault), Wittgenstein, realism, and dialogue between continental and analytic philosophy.

He is the author of A Thing of This World: A History of Continental Anti-Realism, Heidegger’s Later Writings: A Reader’s Guide, Groundless Grounds: A Study of Wittgenstein and Heidegger, Heidegger: Thinking of Being, editor of Division III of Being and Time: Heidegger’s Unanswered Question of Being and Introducing Ethics: A Beginner’s Guide Through Six Major Thinkers, as well as a number of articles and book chapters.

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Philosophy deals with important, enduring questions, yet many of its best ideas remain difficult to access. Academic work is often written for specialists, and few people have the opportunity to study philosophy in a structured course taught by a great teacher.

Ergo aims to make the experience of learning from a great teacher accessible to anyone. Most of our courses run four to eight hours in total. The length is deliberate: long enough to move beyond surface summaries into real substance, yet short enough to watch over a few sittings.

We define philosophy broadly. Our courses cover philosophers from the ancient world to the present, as well as big-picture questions across the arts and sciences. To us, philosophy includes any disciplined attempt to step back and examine a domain’s assumptions, its limits, and how it connects to everything else. Or, as Wilfrid Sellars put it, understanding “how things in the broadest possible sense of the term hang together.”

Today we’re launching with five courses:

From Descartes to Nietzsche: The Birth of Science and the Death of God

Lee Braver traces the development of modern philosophy through Descartes, Hume, Kant, and Nietzsche, showing how each attempt to secure certainty gave way to deeper skepticism about truth itself.

Watch: Website • YouTube

Quantum Mechanics and the Crisis of Scientific Realism

David Albert begins with strange experiments on electrons, builds to the measurement problem, and explores competing answers to one of science’s deepest questions: can quantum mechanics describe reality at all?

Watch: Website • YouTube

Computation as a Universal and Fundamental Concept

Tim Roughgarden treats computation as a law of nature, tracing its arc from Turing’s proof that some problems are unsolvable to the P versus NP question at the heart of modern computer science.

Watch: Website • YouTube

Lectures on Infinity

Joel David Hamkins explores the great paradoxes and discoveries surrounding infinity, from Zeno’s ancient puzzles to Cantor’s revolutionary proof that some infinities are larger than others.

Watch: Website (Complete course) • YouTube (New lectures released monthly)

Plato’s Theaetetus: An Inquiry into Knowledge

Richard Polt guides viewers through Plato’s Theaetetus, asking whether knowledge is perception, whether truth is relative, and what it means to know anything at all.

Watch: Website • YouTube

We hope you’ll explore the courses. Many more are already in the works, and we’ll be releasing new ones regularly. If you’d like to be notified when new courses go live, you can subscribe below.

— The Ergo team

COMING NEXT MONTH:

Introduction to Spinoza and his Theory of Love

Noa Lahav Ayalon traces Spinoza’s philosophy from its metaphysical foundations to his vision of love and human flourishing.

From Socrates to Sartre: How should we live?

Lee Braver walks through the great ethical theories of Western philosophy, from Socrates’ founding questions to Mill, Kant, Aristotle, and Sartre’s radical challenge.

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