o notion could be further away from the fact than the some- what sedulously cultivated idea that the difference between ancient and modern science is that the former had no respect for perception and relied exclusively upon speculation. In fact, the Greeks were keenly sensitive to natural objects and were keen observers. The trouble lay not in substitution of theoriz- ing from the outset for the material of perception, but in that they took the latter "as is"; they made no attempt to modify it radically before undertaking thinking and theorizing about it.