A logical rule-of-thumb, analogous to Occam's Razor. A 'steelyard' is a scale, thus the lighter or least complicated idea rises to the top when balanced against a heavier, more complicated idea.

The word "steelyard" is probably a reference to Orazio Grassi's book of 1619, "The Balance", which weighed Galileo's early works and found them wanting.

Community content is available under CC-BY-SA unless otherwise noted.