Skepticism has been an important topic throughout the history of philosophy and is still widely discussed today. [2] As a philosophical school or movement, skepticism arose both in ancient Greece and India. In India the Ajñana school of philosophy espoused skepticism.

Skepticism has deep roots in philosophical history, dating back to ancient Greece. The Pyrrhonists, led by Pyrrho of Elis, posited that because certainty is unattainable, one should suspend judgment on all matters.

Originally, in ancient Greece, skepticism was the philosophy of questioning all claims, religious, ethical, scientific, or otherwise. The point of skepticism was not so much to disbelieve claims, but to interrogate them; the word skepticism is derived from the Greek skepsis, meaning “inquiry.”

The skeptical tradition originated in the Hellenistic period of ancient philosophy. After mostly lying dormant through much of the medieval era, it was revived and—to some extent—transformed in early modern philosophy.

In ancient times skeptics challenged the claims of Platonism, Aristotelianism, and Stoicism, and in the Renaissance those of Scholasticism and Calvinism. After Ren é Descartes, skeptics attacked Cartesianism and other theories justifying the "new science."