Did Pythagoras Really Call 10 the Holiest Number?

The Tetractys -- the triangular figure made of 10 dots arranged in four rows (1+2+3+4=10) -- was indeed sacred to the Pythagorean school. Followers reportedly swore oaths by it, and it represented the harmony of the cosmos: the first four numbers contained within them the ratios of the basic musical intervals. However, Pythagoras himself was a semi-legendary figure who deliberately cultivated mystery. He wrote nothing down, demanding that his teachings be transmitted orally. Our knowledge of Pythagorean doctrine comes primarily from Aristotle (born ~80 years after Pythagoras died), Diogenes Laertius (writing ~700 years later), and Iamblichus (~800 years later). Each of these writers had their own agendas and interpretive frameworks. The clean, declarative statement that 'the Pythagoreans regarded 10 as the holiest number' is likely a later writer's summary of a complex mystical tradition, not a direct quote.