But while Galen’s monotheism cannot be regarded as of Christian or Jewish origin, it is possible that his argument from design and supporting theology by anatomy made him more acceptable to both Mohammedan and Christian readers. At any rate he had Christian readers at Rome at the opening of the third century, when a hostile controversialist complains that some of them even worship Galen.[606] These early Christian enthusiasts for natural science, who also devoted much time to Aristotle and Euclid, were finally excommunicated; but Aristotle, Euclid, and Galen were to return in triumph in medieval learning. II. _His Medicine and Experimental Science_ [Sidenote: Four elements and four qualities.] Galen held as his fundamental theory of nature the view which was to prevail through the middle ages, that all natural objects upon this globe are composed of four elements, earth, air, fire, and water,[607] and the cognate view, which he says Hippocrates first introduced and Aristotle later demonstrated, that all natural objects are characterized by four qualities, hot, cold, dry, and moist. From the combinations of these four are produced various secondary qualities.[608] Neither hypothesis was as yet universally accepted, however, and Galen felt it incumbent upon him to argue against those who contended that the human body and world of nature were made from but one element.[609] There were others who ridiculed the four quality hypothesis, saying that hot and cold were words for bath-keepers, not for physicians to deal with.[610] Galen explains that philosophers do not regard any particular variety of earth or any other mineral substance as representing the pure element earth, which in the philosophical sense is an extremely cold and dry substance to which adamant and rocks make perhaps the closest approach. But the earths that we see are all compound bodies.[611] [Sidenote: Criticism of atomism.] Galen rejected the atomism of Democritus and Epicurus, in which the atoms were indivisible particles differing in shape and size, but not differing in quality as chemical atoms are supposed to do. He credits Democritus with the view that such qualities as color and taste are sensed by us from the concourse of atoms, but do not reside in the atoms themselves.[612] Galen also makes the criticism that the mere regrouping of “impassive and immutable” atoms is not enough to account for the new properties of the compound, which are often very different from those of the constituents, as when “we alter the qualities of medicines in artificial mixtures.”[613] Thus he virtually says that the purely physical atomism of Democritus will not account for what to-day we call chemical change. He also, as we shall see, rejected Epicurus’ theory of a world of nature ruled by blind chance. [Sidenote: Application of the theory of four qualities in medicine.]