Hello Marco!
Why Ahura Mazda created us? Hmm... I will tell this an other time, if you don't mind. The Gathas, and even the whole of the Avesta, unlike the Torah and the Bible, do not tell the story of creation, at least not progressively: that lets us think what we want about the origins of species. For example, I am a partisan of the evolution theory. The reason of that "absence" is that the sacred Avesta isn't meant to answer to material questions, but rather spiritual ones. This is the reason why there are so few rules concerning daily life in the Avesta.
Ahura Mazda created light first, as it is said the Holy Gathas: "Ahura Mazda's First Thought blazed into myriads of sparks of light and filled the entire heavens.[...]" (31:7). As you see they are 31 Yasnas before that, and four Gathic Yasnas. I think this is the description of the suns. I heard from someone who loves science etc. that in the very beginning of the Universe the first thing that appeared was light, through the creation of suns which were amounts of gases.
Ahura Mazda is "First and Last of all Creation", as repeats Ashu Zarathushtra a few times in the Gathas. I do not know how It "appeared", how It came; and no one knows. If you come in a room and see someone who's already here, how would you know how he has come before you? That's the first point, the second is that in Zoroastrianism, we do not make, unlike Muslims and most of Christians (for example), a clear separation between God, Ahura Mazda, and the entire Universe. I read in the Bah'ai overview in this forum (which was very interesting), that (sorry for the long quote):
"So perfect and comprehensive is His creation that no mind or heart, however keen or pure, can ever grasp the nature of the most insignificant of His creatures; much less fathom the mystery of Him Who is the Day Star of Truth, Who is the invisible and unknowable Essence..."
and further
"All that the sages and mystics have said or written have never exceeded, nor can they ever hope to exceed, the limitations to which man's finite mind hath been strictly subjected. To whatever heights the mind of the most exalted of men may soar, however great the depths which the detached and understanding heart can penetrate, such mind and heart can never transcend that which is the creature of their own thoughts.[...]"
That, is not the Zoroastrian point of view. We think Ahura Mazda is within us, within all the creation, within the Yazata (the "worthy of worship beings"), within all the Universe. Of course Ahura Mazda is not in the evil.
What is the kind of existence of Ahriman is subject to debate among Zoroastrian thinkers and philosophers of all times. Is it alive? Is it a physical being? A mind?
Ahriman is a deformation of "Angra Mainyu" which is in the Gathas. It means "angry mind" -yes, and both those words ("angra" and "mainyu") have the same origin as the English words. "Mind", for example, has the same origin as "mentalité" in French, etc. Zarathushtra tells us there is the Best Mind (Vohu Manangha, Vohu Mana), and the Worst, (Angra Mainyu, Angra Manangha). In the latter Avesta Angra Mainyu has become an anti-Yazat. In the Gathas it is, nevertheless, considered as one principle: the evil principle.
I will quote the great sages who wrote the Dadestan-i Denig ("Religious Decisions") in the 9th century after Jesus Christ:
"1. The eighteenth question is that which you ask thus: When the souls of the righteous and the souls of the wicked go out to the spirits, will it then be possible for them to see Ohrmazd and Ahriman, or not?
2. The reply is this, that concerning Ahriman it is said that his is no material existence. [...]" (19:1-2). They clearly give their point of view, which is: Ahriman is evil; but no devil. Does evil need to have a material existence to be? This I ask you.
How evil appeared is an interesting question, which can easily be answered, quoting the Gathas. There is an entire chapter (Yasna) of the Gathas which is called "The Origin of Evil". Let me quote it:
"Now in the beginning these two mentalities, the twins, revealed themselves in vision
as the better and the bad in thought, word and deed. The wise and the generous chose correctly between these two, but the unwise and the mean did not." 30:3.
"And so when these two mentalities first came together, they established life (gaya) and non-life (ajyaiti). The worst life will be for the Followers of the Lie, but the Supreme Mind of Ahura Mazda will illumine the Followers of Truth." 30:4.
We understand that the good mentality, (Vohu Mana, which is linked to Ahura Mazda) is linked to Truth, while the worst (Angra Mainyu) is linked to the Lie. It is the origin of the hate that every true Zoroastrian feels against the act of lying.
Now about the Followers of both:
"The Daevas (Devils) (and their worshippers) did not discriminate wisely
between these two. Confusion came upon them as they debated,
and so they chose the Worst Mind.
Straightaway, they fell headlong into Wrath. The life of man sickened." 30:6.
Here we do discover that the essence of Daevas and Men is not evil: but Daevas and some men chose evil (in thought word and deed).
"Then the Sovereignty of Ahura came to the just man
through the Good Mind and Truth[...]." 30:7.
I think it is enough to explain a lot, if you have questions about that part, do not hesitate to ask!
Sorry dear Marco "of Ahriman, and if it goes to infinite, then how comes it will vanish some day..." I have not understood, could you rephrase your question, please?
I understood your main point has been dualism. But Zoroastrian dualism has a special aspect, look: the main principles, the only principles are dual (life and death, lie and truth, =good and evil), but in higher spheres, the divine spheres, Ahura Mazda is higher than Angra Mainyu, than Ahriman. Angra Mainyu equals (in power) Vohu Mana, but not Ahura Mazda. The duality is thus a semi-duality. If you want to understand it more accurately you've got to look at the essences in Zoroastrianism.
