This idea was later developed in ancient philosophy by the Stoic school. Stoic epistemology generally emphasized that the mind starts blank, but acquires knowledge as the outside world is impressed upon it. The doxographer Aetius summarizes this view as "When a man is born, the Stoics say, he has the commanding part of his soul like a sheet of paper ready for writing upon." Later stoics, such as Sextus of Chaeronea, would continue this idea of empiricism in later Stoic writings as well. As Sextus contends "For every thought comes from sense-perception or not without sense-perception and either from direct experience or not without direct experience" (Against the Professors, 8.56-8).