An ancient philosophy, named for its inventor. It consisted of an absolute disbelief in everything but Pyrrhonism. Its modern professors have added that.

Skepticism; universal doubt.

Pyrrhonism, or Pyrrhonian skepticism, was a school of skepticism founded by Aenesidemus in the first century BCE and recorded by Sextus Empiricus in the late 2nd century or early 3rd century CE. It was named after Pyrrho, a philosopher who lived c. 360 to c. 270 BCE, although the relationship between the philosophy of the school and of the historical figure is murky. Pyrrhonism became influential during the past few centuries when the modern scientific worldview was born.