Here I will consider natural science only insofar as it is grounded on empirical principles.b When Galileo' rolled balls of a weight chosen by himself down an inclined plane, or when Torricelli' made the air bear a weight that he had previously thought to be equal to that of a known column of water, or when in a later time Stahl's changed metals into calxc and then changed the latter back into metal by first removing something and