No, the above argument leaves room for diminishing returns - it only assumes that spending more time learning foo is more efficient at learning foo than spendin

No, the above argument leaves room for diminishing returns - it only assumes that spending more time learning foo is more efficient at learning foo than spending more time learning bar is at learning foo. Suppose Alice and Bob have similar levels of talent. Alice spent 10000 hours learning the piano. Bob spent 2000 hours learning the piano, 2000 learning the violin, 2000 learning percussion, 2000 learning to sing and 2000 writing a novel. The above argues that Alice will be better at playing the piano than Bob. Probably not five times better (assuming that could be defined in a sensible fashion) - there are diminishing returns - but still better.