"Parsism is decidedly dualistic, not in the sense of accepting two hostile deities, for it recognizes no worship of evil beings, and teaches the adoration only of Ahura Mazda and the spirits subject to him; but in the sense of placing in hostility to each other two sharply divided kingdoms, that of light, of truth, and of purity, and that of darkness, of falsehood, and of impurity. This division is carried through the whole creation, organic and inorganic, material and spiritual. Above, in the highest sphere, is the domain of the undisputed sovereignty of the All-wise God; beneath, in the lowest abyss, the kingdom of his mighty adversary; midway between the two lies this world, the theatre of the contest.... This dualism further dominates the cosmogony, the cultus, and the entire view of the moral order of the world held by the Mazda worshippers. Not only does Anro-Maînyus (Ahriman) spoil by his counter-creations all the good creations of Ahura-Mazda (Ormuzd), but by slaying the protoplasts of man and beast, he brings death into the world, seduces the first pair to sin, and also brings forth noxious animals and plants. Man finds himself, in consequence, surrounded on all sides by the works of the spirits of darkness and by his hosts. It is the object of worship to secure the pious against their influence."
Let us bring in review some of the points of resemblance between the two systems. Both are in a sense dualistic. In both the kingdoms of Light and Darkness are set over against each other in the sharpest antagonism. In both we have similar emanations from these kingdoms (or kings). Yet, while in the Manichæan system the dualism is absolute and eternal, in the later Zoroastrian system (as in the Jewish and Christian doctrine of Satan), Ahriman (Satan) if not merely a fallen creature  of Ormuzd (the good and supreme God) was at least an immeasurably inferior being. The supreme control of the universe, to which it owes its perfect order, was ascribed by Zoroastrianism to Ormuzd. The struggle between good and evil, beneficent and malevolent, was due to the opposition of the mighty, but not almighty, Ahriman. Whatever form of Mazdeism (Zoroastrianism) we take for purposes of comparison, we are safe in saying that the Manichæan dualism was by far the more absolute.
In both systems each side of the dualism is represented by a series (or rather several series) of personified principles. These agree in the two systems in some particulars. Yet the variations are quite as noticeable as the agreements. There is much in common between the Manichæan and the Zoroastrian delineations of the fearful conflict between the Kingdom of Light and the Kingdom of Darkness, yet the beginning of the conflict is quite differently conceived of in the two systems. In Manichæism the creation is accounted for by the conflict in which Primordial Man was beaten by the powers of Darkness and suffered the mixing of his elements with the elements of darkness. The actual world was made by the good God, or rather by his subordinates, as a means of liberating the imprisoned light. The creation of man is ascribed, on the other hand, to the King of Darkness (or his subordinates), with a view to hindering the escape of the mingled light by diffusion thereof through propagation. Mazdeism derives the creation solely from Ormuzd, from whose hand it issued "as pure and perfect as himself" (Lenormant, Anc. Hist. II. p.30). It was the work of Ahriman to "spoil it by his evil influence." The appellation "Maker of the material world" is constantly applied to Ormuzd in the Vendîdâd and other sacred books. The most instructive Mazdean account of the creation that has come down to us is that contained in the Vendîdâd, Fargard I. Ahura Mazda (Ormuzd) is represented here as naming one by one the sixteen good lands that he had created. Angra Mainyu (Ahriman) is represented as coming to each, one by one, and creating in it noxious things. Examples of these counter-creations are, the serpents, winter, venomous flies, sinful lusts, mosquitoes, pride, unnatural sin, burying the dead, witchcraft, the sin of unbelief, the burning of corpses, abnormal issues in women, oppression of foreign rulers, excessive heat, etc. This jumble of physical evils and sins is characteristic of Mazdeism.
According to Mani matter is inherently evil, and it only ceases to be absolutely evil by the mixture with it of the elements of the Kingdom of Light. Creation is a process forced upon the King of Light by the ravages of the King of Darkness, and is at best only partially good. Zoroastrianism looked upon earth, fire, water, as sacred elements, to defile which was sin of the most heinous kind. Manichæism regarded actual fire and water as made up of a mixture of elements of light and darkness, and so, as by no means wholly pure. Manichæans regarded earth, so far as it consisted of dead matter, with the utmost contempt. The life-giving light in it was alone thought of with respect. Zoroastrianism somewhat arbitrarily divided animals and plants between the kingdoms of Ormuzd and Ahriman; but the idea that all material things, so far as they are material, are evil, seems never to have occurred to the early Mazdeists. Manichæans agreed with Mazdeists in their veneration for the sun, but the principles underlying this veneration seem to have been widely different in the two cases. The most radical opposition of the two systems is seen in their views of human propagation. Mani regarded the procreation of children as ministering directly to the designs of the King of Darkness to imprison the light, and so absolutely condemned it. The Zend-Avesta says: (Vendîdâd, Fargard IV.): "Verily I say unto thee, O Spitama Zarathustra; the man who has a wife is far above him who begets no sons; he who keeps a house is far above him who has none; he who has children is far above a childless man." Mani made great merit of voluntary poverty. The Zend-Avesta (ibid.) says: "He who has riches is far above him who has none." Mani forbade the use of animal food as preventing the escape of the light contained in the bodies of animals. The Zend-Avesta (ibid.): "And of two men, he who fills himself with meat is filled with the good spirit much more than he who does not do so; the latter is all but dead; the former is above him by the worth of an Asperena, by the worth of a sheep, by the worth of an ox, by the worth of a man." 
The eschatology of the two systems might be shown to present just as striking contrasts, and just as marked resemblances. In both systems the consummation of the age is effected by means of a conflagration, the aim of the conflagration in Mazdeism being the punishment and the purging of wicked men, the destruction of wicked spirits, the renovation of the earth, and the inauguration of the sole sovereignty of Ormuzd, while in Manichæism the aim of the conflagration is to liberate the portions of light which the processes of animal and vegetable growth, with the aid of sun and the moon have proved unable to liberate.
But enough has been said to make it evident that Manichæism was by no means a slightly altered edition of Zoroastrianism. The points of similarity between the two are certainly more apparent than real, though the historical relationship can by no means be denied.
 Outlines of the Hist. of Religion (1877), p. 173. Cf. J. Darmsteter, Introduction to the Zend-Avesta, p. xliii., xliv., lvi., lxxii., lxxiv. sq.; and his article in the Contemporary Review (Oct. 1879), on "The Supreme God in the Indo-European Mythology."  This is confidently asserted by Kessler (Art. Mani in Herzog's RE, 2d ed. vol. IX. p. 258), and after him by Harnack, Encyclopædia Britannica, art. Manichæism. On the other hand, Lenormant (Anc. Hist. II. p. 30), says: "Ahriman had been eternal in the past, he had no beginning, and proceeded from no former being * * * . This being who had no beginning would come to an end. * * * . Evil then should be finally conquered and destroyed, the creation should become as pure as on its first day, and Ahriman should disappear forever." Such, doubtless, was the original doctrine, but the form probably in vogue in the time of Mani was more pantheistic or monotheistic, both Ormuzd and Ahriman proceeding from boundless time (Zrvan akarana). See on this matter, Darmsteter: Introd. to the Zend-Avesta, p. lxxii, etc., and his art. in Contemp. Review; and Lenormant: Anc. Hist. as above.  That meat is used in the sense of flesh may be inferred from Darmsteter's comment on this passage, which he suggests may be a bit of religious polemics against Manichæism. See his Introd. to the Zend-Avesta, p. xl. sq.
 This is confidently asserted by Kessler (Art. Mani in Herzog's RE, 2d ed. vol. IX. p. 258), and after him by Harnack, Encyclopædia Britannica, art. Manichæism. On the other hand, Lenormant (Anc. Hist. II. p. 30), says: "Ahriman had been eternal in the past, he had no beginning, and proceeded from no former being * * * . This being who had no beginning would come to an end. * * * . Evil then should be finally conquered and destroyed, the creation should become as pure as on its first day, and Ahriman should disappear forever." Such, doubtless, was the original doctrine, but the form probably in vogue in the time of Mani was more pantheistic or monotheistic, both Ormuzd and Ahriman proceeding from boundless time (Zrvan akarana). See on this matter, Darmsteter: Introd. to the Zend-Avesta, p. lxxii, etc., and his art. in Contemp. Review; and Lenormant: Anc. Hist. as above.
 That meat is used in the sense of flesh may be inferred from Darmsteter's comment on this passage, which he suggests may be a bit of religious polemics against Manichæism. See his Introd. to the Zend-Avesta, p. xl. sq.