The influence of the Christian religion is further shown and that of the Bible in particular is manifested by numerous allusions to Adam and the earliest period of Biblical history, but very few of them find any justification in the scriptural narrative. Thus the _Liber divinorum operum_ states[384] that after the fall of Adam and before the deluge the sun and moon and planets and other stars were “somewhat turbulent from excessive heat,” and that the men of that time possessed great bodily strength in order that they might endure this heat. The deluge reduced the temperature and men since have been weaker. In the preface to the fifth book of the _Subtleties_ we are told that there are certain plants which fish eat, and which, if man could procure and eat, would enable him to go without food for four or five months. Adam used to eat them at times after he had been cast out of Eden, but not when he could get enough other food, as they make the flesh tough. In the preface to the eighth book Hildegard says that all creatures were good before Adam’s fall, but when Abel’s blood stained the soil noxious humors arose from which venomous and deadly reptiles were generated. These perished in the deluge, but others were generated from their putrefying carcasses. In the _Causae et curae_, too, the names of Adam and Eve occasionally appear in the chapter headings, for instance, “Of Adam’s fall and of melancholy.”[385] [Sidenote: Spiritual lessons from natural phenomena.] Hildegard also held the view, common among medieval Christian writers, that one purpose of the natural world about us is to illustrate the spiritual world and life to come, and that invisible and eternal truths may be manifested in visible and temporal objects. In the _Scivias_ she hears a voice from heaven saying, “God who established all things by His will, created them to make His Name known and honored, not only moreover showing in the same what are visible and temporal, but also manifesting in them what are invisible and eternal.”[386] But neither Hildegard nor medieval Christians in general thought that the only purpose of natural phenomena and science was to illustrate spiritual truth and point a moral. But this always constituted a good excuse which sounded well when one of the clergy wished to investigate or write about things of nature. Not that we mean to question the sincerity of the medieval writers one whit more than that of certain “Christian colleges” of the present which deem it wise to demonstrate their piety and orthodoxy by maintaining compulsory chapel attendance and holding an occasional “Convocation.” But certainly our abbess of Bingen in the course of her writings, especially the _Subtleties_ and _Causae et curae_, lists many natural phenomena and medical recipes without making any mention of what spiritual truth they may or may not illustrate. [Sidenote: Hildegard’s attitude toward magic.]