Religion has been defined as a system of doctrine and worship, which its adherents regard as having divine authority [Bettany]. Some religious scholars of the late ninetieth and early twentieth centuries believed that religion began with animism (belief in spirits), then evolved into polytheism (belief in many gods) and ultimately emerged as monotheism (belief in one god). Other scholars held that religion began with a sense of awe at the impressive activities of nature, such as volcanoes and earthquakes, or in a feeling of reverence for the spirits of the dead, or in an attempt to overcome mortality [Encarta]. Most religions teach systems of morality in order to encourage conformity and cooperation and to discourage nonconformity and cheating. In some religions, ethic of self-sacrifice has functioned to encourage loyalty to a group, thereby tactically promoting human survival. All religions teach virtues, such as love, self-control, compassion, nonviolence, and wisdom, but differences in belief systems can give varying significance to these virtues.

Zoroastrian religion can be termed as ‘natural’, which is the innate capacity of all human beings to arrive at a belief in the existence of a supreme being. Charles Townes, a professor at the University of California in Berkeley, Life Fellow of the Institute of Electrical and Electronic Engineers (IEEE) and a Nobel Laureate in physics, recently won the 1.5 million dollar Templeton Prize for progress in spiritual knowledge. He said that, “The fact that the universe had a beginning is a very striking thing. How do you explain that unique event without God? " Natural religion has compared favorably with the supernatural religions that deem mystical union with the divine. Zoroastrian religion is liberal, comforting, egalitarian and contemplative, and encourages reliance on personal responsibility. A Zoroastrian cannot achieve deliverance either through states of trance, dreams, visions and healings, or through special signs and miracles, mystical experiences, offerings and sacrifices, purification and penance. In some religions, possession of the human body by a mystical entity is a common form of interchange with the spiritual world. However, for every Zoroastrian, relationship with God can only be expressed in terms of moral behavior because each individual has the capability to contribute and improve the quality of human life and thus renew this world.

More than 3000 years ago, Zarathushtra revealed to mankind that there is only One God whom he referred to as Ahura Mazda, literally meaning, “A Being having Super-Wisdom”.  According to Zarathushtra, Ahura Mazda created the universe in space and time through his creative faculty Spenta Mainyu (Best Mentality), perhaps by causing the Big Bang. Ahura Mazda not only let the universe evolve into inanimate objects such as the sun, moon, stars and planets but also into living species such as the plants, animals and human beings. The physical laws, such as the principles of gravity and electromagnetism came into existence, and natural selection which can weed out potentially dangerous genetic mutations govern the evolution of the universe to this day. 

The Gathas, composed by Zarathushtra, refer to Ahura Mazda as “Tashô” (Yasna 31-11), which signifies a designer and conveys the idea of improvement, progress and evolution. Ahura Mazda is not only the creator but also the maintainer and promoter of his creations. In the Gathas, Zarathushtra also describes other attributes of Ahura Mazda. These are Vohu Manah (intelligent and good thinking), Asha (truth and righteousness), Khshathra (benevolent power and rule of goodness), Armaiti (tranquility and serenity), Haurvatat (perfection and completeness) and Ameratat (immortality). 

Zarathushtra introduced the unique idea that the purpose for human life is to emulate the attributes of Ahura Mazda and help move His creation towards perfection. Ahura Mazda is intelligent and full of wisdom and has vouchsafed every human being with Vohu Manah, a good mind, so that we can think and discern what is good and bad, and rationally choose our own path in life. The human mind is the best gift that has been bestowed on us by Ahura Mazda and we are the only species in the animal kingdom capable of assessing rationally and discriminating good from evil. By employing our mind we can be creative, constructive and progressive or unimaginative, destructive and ignorant. The freedom to choose between, good and evil is the underlying principle of Zarathushtra’s religion (Y 30.2):

We should make our choices only after listening and reflecting and not make decisions based on popularity or because we are coerced to do so. Recently, a team of neuroscientists at Imperial College of London used MRI to study the response of the brain to the decision making process. To their surprise they discovered that only the medial frontal cortex was active when people freely made choices, but other parts of the brain became active when people were forced to make certain decisions. Their study was recently published in the journal Current Biology. Human beings are co-workers of Ahura Mazda, but not his slaves because Zarathushtra does not implore blind faith but a reflective philosophy based on knowledge and learning.

The dualism reflected in the Gathas is not cosmic but moral; for good and evil are confined to the human mind, and thoughts, when translated into words and actions can produce good or bad results. Zoroastrianism is an ethical religion and teaches that mortals can achieve spiritual completeness by fighting evil with Humata, Hukhta and Havarashtra (good thoughts, good words and good deeds).

According to Zarathushtra the universe is regulated through Asha or Arta, the old Indo-Iranian law of "truth and precision". At the physical level Asha represents the laws in the universe and scientists try to understand these laws of physics, chemistry and biology. On the psychological level Asha is the powerful force of truth while at the spiritual level Asha is the fusion of order and truth leading us to the path of righteousness. Goodness, benevolence and knowledge are an integral part of what is right, and Asha represents not only law and social order but also scientific, philosophical and spiritual truth. Asha is doing the right thing, at the right time, in the right place with the right means to achieve the right purpose [Dhalla]. The Ashem Vohu prayer declares that happiness comes to the one who is virtuous and performs good deeds for the sake of virtue: