Introduction
Vohu Manah, "Good Purpose" or "Good Mind" (later Bahman), is one of the six Amesha Spentas, representing right thought and benevolent purpose, and traditionally associated with the protection of cattle and beneficial animals.
The Amesha Spentas ("Bounteous Immortals") are six (or, counting Ahura Mazda himself as their head, seven) divine beings who represent and administer aspects of Ahura Mazda's good creation. Zoroastrian theology generally treats them as emanations or aspects of Ahura Mazda's own nature rather than as separate offspring in an ordinary genealogical sense, and each is opposed by one of the six chief daevas in Zoroastrian dualism.
Zarathustra's vision
In Zoroastrian tradition, Vohu Manah is the Amesha Spenta who first appeared to Zarathustra and led him into the presence of Ahura Mazda, making him, in a sense, the gateway through which the prophet received his revelation, and a figure closely associated with the beginning of the Zoroastrian faith itself.
Domain
Vohu Manah's association with cattle reflects the importance of livestock in ancient Iranian pastoral society, and by extension, he represents the broader principle of good, careful thought applied to the proper use and treatment of the created world's good things.
Opposing daeva
Vohu Manah is opposed in Zoroastrian dualism by Aka Manah, "Evil Mind" or "Evil Purpose", one of the six chief daevas, who represents corrupted thought and malicious intent.