The concept of evil twins is ancient and mythical. One of the earliest may be in the Zurvanite branch of Zoroastrianism. This sect distilled the general abstract duality of Zoroastrianism into a concept of manifest twins "born" of a monist (first) principle "Zurvan" (Time). In this cosmological model, the twins—Ahura Mazda (Ormuzd) and Angra Mainyu (Ahriman)—were co-eternal representatives of good and evil. Ahura Mazda, representing good, was eventually expected to win the battle. The doctrinal foundation of Zurvanism lies in its interpretation of the Zoroastrian precepts of Free Will: Like Mazdaism (the other, and still extant branch of Zoroastrianism), Zurvanism emphasized that mortals always "have a choice between good and evil, and that one is always free to make the choice one way or the other." Zurvanism took this one step further and considered Angra Mainyu "evil" by choice, rather than by nature. This characterization is important to modern uses of the "evil twin", as most examples are in fact opposites of their "good twin", rather than wholly evil.