Skepticism, as a philosophical school of thought, has endured for over two millennia not by offering certainties, but by persistently questioning them. This book is an exploration of skepticism—not as a rejection of knowledge, but as a method of inquiry, a disciplined doubt, and a guide for navigating the boundaries of belief and understanding.

From its roots in ancient Greece to its reverberations in modern epistemology and science, skepticism has played a crucial role in shaping the intellectual history of the West. Figures like Pyrrho, Sextus Empiricus, and later René Descartes and David Hume, each in their own way, questioned the reliability of perception, the trustworthiness of reason, and the foundations of knowledge itself. But skepticism is not monolithic. There are radical skeptics, who doubt the possibility of knowledge altogether, and mitigated or academic skeptics, who temper doubt with practical engagement in the world.

This book does not aim to champion skepticism as the final philosophical stance, nor to dismiss it as an intellectual dead end. Instead, it presents skepticism as a vital tradition that serves an indispensable role in philosophy: it compels us to re-examine our assumptions, to clarify our justifications, and to resist the seduction of easy answers. In a world increasingly saturated with information and opinion, skepticism reminds us that the mere possession of data does not equate to wisdom—and that humility in the face of uncertainty is a virtue, not a weakness.

The structure of this book reflects the breadth and evolution of skeptical thought. It begins with the historical foundations—tracing the origins of skepticism in ancient Greek philosophy, particularly in Pyrrhonism and the Academic Skeptics. It then explores how skepticism was received and reinterpreted by medieval thinkers and transformed during the Enlightenment. Particular attention is given to Descartes’ methodological doubt, which paradoxically used skepticism to seek indubitable truths, and Hume’s empiricist skepticism, which challenged the very coherence of causality and the self.

The book then shifts to contemporary engagements with skepticism, especially in the realms of epistemology, science, ethics, and even technology. Here, we confront questions that are as pressing today as they were in antiquity: What can we know? How do we know it? And what should we do when certainty is out of reach? These questions are not just abstract puzzles for philosophers; they underlie our political discourse, scientific progress, and personal decisions.

Skepticism is often misunderstood as cynicism or nihilism. But genuine philosophical skepticism is neither despairing nor paralyzing. It is an attitude of critical vigilance. It refuses to accept belief without adequate justification and demands that truth be earned, not assumed. It is uncomfortable, often inconvenient—but profoundly necessary.

As you read through these pages, I invite you not merely to observe the skeptical tradition from a distance, but to engage with it actively. Allow yourself to doubt, to question, and to reconsider what you think you know. Whether you emerge from this book more skeptical or more confident in your beliefs is less important than whether you have learned to examine them more carefully.

Philosophy begins in wonder, but it survives through skepticism. This book is a journey into that skeptical spirit—a spirit that challenges us not to settle for certainty, but to strive, always, for understanding.

Pons Malleus

Livros