Thus is dualism established and determined; thus the concept of it develops through the slow travail of the ages from the concept that men have both of nature and of themselves. However, this history that I have hinted at is, so to speak, the schematic and ideal history of dualism, not the concrete and real one. Dualism is found, either fully developed or in embryo, either expressed or implied, in all, or nearly all, religions; but it moves in different planes, takes on various forms, and in varying manners it expresses itself, conforming to the diversity of the world’s civilisations.

      We have seen that maleficent spirits already appear in the rudest and least differentiated religions; but ill-defined and, as it were, diffused among objects. In the loftier religions, as their organic structure becomes circumscribed and complete, the maleficent spirits show themselves better defined, they begin to acquire attributes and personality. Among the great historic religions, that of ancient Egypt is the one of which we possess earliest and surest knowledge. Over against Ptah, Ra, Ammon, Osiris, Isis and others – beneficent divinities, bestowers of life and prosperity – are set the serpent Apepi, personifying impurity and darkness, and dread Set, the ravager, the troubler, father of deceit and of lies. The Phoenicians opposed to Baal and Asherah, Moloch and Astarte; in India, Indra the begetter and Varuna the preserver had, as their opposites, Vritra and the Asuras, and dualism even forced its way into the Trimurtri itself; in Persia, Ormuzd had to contend with Ahriman for the lordship of the world; in Greece and in Rome, a whole race of maleficent genii and monsters rose against the divinities of Olympus (themselves not always beneficent), and there appeared Typhon, Medusa, Geryon, Python, evil demons of every sort, lemures and larvae. Dualism likewise appears within the Germanic mythology, the Slavic, and, in general, in all the mythologies.

      In no other of the ancient or modern religions has dualism the full and conspicuous form that it attained in Mazdaism, the religion of the ancient Persians, as revealed to us through the Avesta; but in all these religions it can be perceived, and in all, to some degree at least, it can be connected with the great natural phenomena, with the alternation of day and night, with the interchange of the seasons. The various concepts, images and events wherein it takes form and reveals itself furnish a picture, not only of the character and civilisation of the people that give it a place in the system of their own beliefs, but also of their climate, of the natural conditions of their soil, of the changes in their history. The dweller of a torrid region recognises the work of the evil spirit in the wind of the desert which scorches the air and blasts the standing corn; the dweller of the northern shores recognises it in the frost that benumbs all life around him and threatens him with death. Where the earth is rocked with frequent earthquakes, where volcanoes belch forth destructive ashes and lava, man easily imagines subterranean demons, wicked giants buried beneath the mountains, the vents of the infernal regions; where frequent tempests convulse the heaven, he imagines demons that fly howling through the air. If an enemy invades the land, subdues and conquers it, the conquered people will not fail to transfer to the evil spirit, or spirits, the most hateful of the characteristics of the oppressor. Thus, religion is the composite result of a multiplicity of causes, which cannot always, it is true, be traced and pointed out. The Greeks really had no Satan, neither had the Romans; and it may appear strange that the latter, who deified a great number of abstract concepts, such as youth, concord, chastity, never imagined a true divinity and power of evil, even though they did imagine a goddess Robigo, a goddess Febris and others of like character.[5] Nevertheless, there are not lacking in the religions of the Greeks and Romans antagonistic powers and figures that present a sort of double aspect; and if one delves a little more deeply into the character of the two peoples, and into their living conditions and their history, he sees that among them dualism could not have assumed a form very different from that which it actually did take. Let it be borne in mind, furthermore, that in Greece and in Rome there was no sacred book of morals, no theocratic code properly so called.

      Dualism takes on form and special characteristics, first in Judaism, next in Christianity; and though in other religions, even in the primitive ones, there may be discerned a sort of phantom of Satan, a sort of form which – to borrow a term from chemistry – might be called allotropic, a form variously named, sometimes enlarged, the real Satan, with the qualities that are peculiarly his own and that go to make up his personality, belongs only to these two religions, and more particularly to the second one.

      Satan holds, as yet, only a humble position in the Mosaic system; I might say that there he merely reaches his childhood or adolescence, without being able to arrive at maturity. In Genesis, the serpent is merely the most subtle and cunning of the beasts,[6] and only by virtue of a late interpretation is he transformed into a demon. The whole Old Testament recognises Beelzebub only as a divinity of the idolaters;[7] in which connection it is worth noting that the Hebrews, before they came to deny the existence of the gods of the Gentiles – a decision that they were very late in reaching – , believed that these were indeed gods, but less powerful and less holy than Jehovah, their own national god. In fact, the first commandment of the Decalogue does not say, “I am thy God, and thou shalt not believe that there are any other gods beside me,” but rather, “I am thy God, and thou shalt not worship any other gods beside me”. Now it is well-known that many times the Hebrews did suffer themselves to be drawn away to worship other gods than their own. Azazel,[8] the unclean spirit to whom in the wilderness was turned over the scapegoat, laden with the sins of Israel, very probably belongs to a system of beliefs anterior to Moses; but his figure lacks clarity and outline, and perchance he is nothing more than a pale reflection of the Egyptian Set and a memory of the years of bondage endured in the land of the Pharaohs.

      It is a commonly accepted opinion that only after the Babylonian captivity did the Hebrews have any clear and precise ideas regarding demons. Finding themselves, during that period, in continuous if not intimate contact with Mazdaism, the Hebrews had the opportunity to learn certain of its teachings and, in part, to adopt them; and among these doctrines, that concerning the origin of evil must have found easy access to their minds, prepared and predisposed as they were by their recent misfortunes and by forebodings of a gloomy future. Such an opinion leaves room for some doubt, and more than one objection can be raised against it; nevertheless, it is no less certain that, if the idea of maleficent spirits and a belief in their workings were not lacking among the Hebrews before the exile, Satan does not begin to take on the figure and characteristics that are peculiar to him save in writings that are posterior to the exile itself. In the Book of Job, Satan still appears among the angels in Heaven[9] and is not properly a contradicter of God and a hinderer of His works. He doubts the holiness and constancy of Job and provokes the test that is to plunge him from the height of happiness to the lowest depth of misery. Notwithstanding this, he is not a fomenter of sin and worker of woe; yet he does doubt holiness, and some of the ills that befall the innocent patriarch come from him.

      Little by little, Satan grows and becomes complete. Zechariah represents him as an enemy and accuser of the chosen people, eager to defraud them of divine grace.[10] In the Book of Wisdom, Satan is a disturber and corrupter of the work of God; he it was who through envy impelled our first parents to sin.[11] He is the poison that wastes and defiles creation. But in the Book of Enoch, and particularly in the older part of it, the demons are merely enamoured of the daughters of men and thus