Journey · 10 stops
Doubt and the Self
From ancient skepticism to the modern subject – and its critics.
Stops
Stop 1 of 10: Sextus Empiricus
Can we know anything for certain? Sextus Empiricus, a Greek physician of the 2nd century, collects the arguments of Pyrrhonian skepticism: to every argument an equally strong one can be opposed. Since we cannot decide, the skeptic suspends judgment – and finds peace of mind in doing so. For centuries these writings lie almost unread in the Latin West.
Stop 2 of 10: Michel de Montaigne
When Sextus’ Outlines appear in Latin in 1562, Montaigne reads them closely and has skeptical maxims painted on the beams of his library. He turns doubt inward: in his Essays he tests his own judgment and asks “Que sais-je?” – What do I know? Doubt becomes a way of life, tolerant and personal; it takes Descartes to turn it into a method.
Stop 3 of 10: Meditations on First Philosophy
Descartes knows the skeptics and Montaigne well, and he pushes doubt to the limit in order to defeat it. In the Meditations he doubts the senses, the body, even mathematics – until one certainty remains: while I doubt, I think, and so I am. On this thinking self he wants to rebuild all knowledge; how it reaches the world becomes the problem for everyone after him.
Stop 4 of 10: John Locke
Locke rejects Descartes’ innate ideas: the mind begins as a blank slate, and everything in it comes from experience. Where Descartes started from the certainty of the thinking self, Locke starts from sensation and reflection – and grounds personal identity in the continuity of consciousness and memory. But if all we have are ideas from experience, how much can they tell us about the world, or about the self?
Stop 5 of 10: David Hume
Hume follows Locke’s empiricism to its end – and finds less than expected. Looking inward, he catches no self, only a bundle of perceptions; looking outward, no necessary connection between cause and effect, only habit. The skepticism of Sextus returns in modern form, now aimed at reason itself. Hume settles for nature and custom, but leaves philosophy a question it cannot ignore.
Stop 6 of 10: Critique of Pure Reason
Kant, by his own account woken by Hume from his “dogmatic slumber”, accepts that causality cannot be read off experience – and turns the problem around. Space, time and the categories are conditions the subject brings to all experience; that is why they hold necessarily. The self returns, not as Descartes’ thinking substance but as the “I think” that must be able to accompany all our representations.
Stop 7 of 10: Edmund Husserl
Husserl, drawing on both Descartes and Kant, returns to the subject with a new method. Suspend every assumption about the world – the epoché – and describe what appears exactly as it appears: consciousness is always consciousness of something. One of his books is even titled Cartesian Meditations. But can a consciousness bracketed off from the world really be the starting point?
Stop 8 of 10: Being and Time
Heidegger, Husserl’s assistant and later his successor in Freiburg, answers no. In Being and Time he argues that we are never first a consciousness facing an outer world, but always already Being-in-the-world – handling things, caring, mortal. The Cartesian subject loses its role as foundation. A generation later, in Oxford, the same picture comes under attack from a quite different side.
Stop 9 of 10: The Concept of Mind
Gilbert Ryle attacks the Cartesian picture with the tools of ordinary-language analysis: the mind is not a “ghost in the machine” but a matter of how we act and are disposed to act. In the same years Wittgenstein, in Cambridge, was asking what certainty itself rests on.
Stop 10 of 10: On Certainty
Wittgenstein’s last notes, written in 1949–51 and published as On Certainty (1969), take up G. E. Moore’s claim to know that “here is one hand”. Such certainties, Wittgenstein replies, are not knowledge won against the sceptic but the hinges on which our questions turn: doubt itself needs ground that is not doubted. From Sextus’ suspended judgment to here, the journey traces how doubt created the modern self – and how that self, once the secure foundation, became the very thing most in question.
As of November 2026 · Improve this page · How Agora is made