Throughout the _Natural Questions_ Adelard’s explanations and answers are based in large measure upon the familiar hypothesis of the four elements and of the four qualities, hot and cold, dry and moist. When asked, for instance, why all ruminating animals begin to lie down with their hind legs, he explains that their scanty animal heat is the cause of their ruminating to aid digestion, and that there is more frigidity in their posterior members, which are consequently heavier and so are bent first in reclining. The nephew thinks that here he has caught his uncle napping, and asks why is it then that in rising they lift themselves first onto their hind legs. But Adelard is not to be so easily nonplussed, and explains that after they have lain down and rested, they feel so refreshed that they lift their heavier limbs first.[75] Again, asked why persons of quick perception often have faulty memories, Adelard suggests that a moist brain is more conducive to intelligence, but a dry one to memory. Thus moist potter’s clay receives impressions more readily but also easily loses them; what is drier receives the impression with more difficulty but retains it.[76] In a third passage, Adelard explains his nephew’s weeping in his joy at seeing his uncle safely returned by the theory that his excessive delight overheated his brain and distilled moisture thence.[77] [Sidenote: Refinement of the four elements hypothesis.] Adelard, however, like Galen, Constantinus Africanus, Basil, and other writers before him, finds it advisable to refine the theory of the four elements. He is at pains in his answer to the nephew’s very first question to explain that what we commonly call earth is not the element earth, and that no one ever touched the pure element water, or saw the elements air and fire. Every particular object contains all four elements and we deal in daily life only with compounds. In an herb, for instance, unless there were fire, there would be no growth upward; unless there were water or air, no spreading out; and without earth, no consistency. Moreover, when Adelard is asked why some herbs are spoken of as hot by nature, although all plants have more earth than fire in their composition, he says that while earth predominates quantitatively, efficaciously they are more fiery, just as his green cloak is larger than his green emerald, but much less potent.[78] Thus comes in the theory of occult virtue to help out the inadequate and unsatisfactory hypothesis of four elements and four qualities. We shall find our subsequent authors often resorting to the same explanation. [Sidenote: Animal intelligence doubted.]