"The observation and experiments necessary for the pursuit of alchemy did not comport with the Greek idea of philosophy. This is shown by the saying of Socrates, that the nature of external objects could be discovered by thought without observation, and by the renunciation of all natural sciences by the Cynics. This came largely from the fact that they saw in the nature around them the mutable only. Plato separated logic, as the knowledge of the immutable, from physics, the knowledge of the mutable. That which was subject to indefinite change would not repay observing nor recording, therefore they could not conceive of astronomy and physics as serious objects of mental occupation. There was nothing to be learned from fields and trees and stones. One of the philosophers is said to have gone to the length of putting out his eyes, in order that his mind might not be influenced by external objects, but might wholly give itself to pure contemplation. The intellectual power and grasp of these philosophers were wonderful, but faulty and misleading, since the real and practical was left out."