Monotheism is the religious belief that only one God exists. It stands in contrast to polytheism, which recognizes the existence of multiple deities. The term comes from the Greek monos, meaning “alone” or “one,” and theos, meaning “god.”
In a monotheistic religion, God is regarded as a single, unique reality that cannot be divided into several independent gods. God is often described as the creator of the universe, the source of all existence, and the supreme authority. However, monotheistic religions do not all share the same understanding of God’s nature, attributes, or relationship with human beings.
The three religions most commonly associated with monotheism are Judaism, Christianity, and Islam. They are also known as the Abrahamic religions because all three, although in different ways, recognize Abraham as an important figure.
In Judaism, the oneness of God is a fundamental principle. It is notably expressed in the Shema Yisrael, a central Jewish prayer proclaiming God’s unity. God is regarded as the creator of the world and the God of the Covenant with the people of Israel. God cannot be represented by a material image, and the relationship between God and human beings is expressed particularly through the Torah and its commandments.
Christianity also affirms the existence of one God. Most Christian Churches, including Catholic, Orthodox, and Protestant denominations, teach the doctrine of the Trinity. According to this understanding, God is one but exists in three persons: the Father, the Son, and the Holy Spirit. For these Churches, this does not mean three gods, but one God in three distinct persons. Some Christian movements, such as Unitarianism, reject this doctrine and uphold a strictly unitarian understanding of God.
In Islam, divine oneness is expressed through the concept of tawhid. God, called Allah in Arabic, is absolutely one and has no partners. This affirmation occupies a central place in the Muslim profession of faith, the shahada, which declares that there is no deity but God. Islam recognizes Abraham, Moses, and Jesus, among others, as prophets, but rejects the idea that Jesus is himself God.
Monotheism, however, is not limited to these three religions.
Sikhism, which emerged in northern India towards the end of the 15th century, affirms the existence of a single, eternal divine reality present throughout creation. This idea is expressed through the formula Ik Oankar, which appears at the beginning of the Guru Granth Sahib, the sacred scripture of the Sikhs. The Sikh Research Institute emphasizes that this divine reality is not confined to any particular community but concerns all humanity.
The Bahá’í Faith, which originated in 19th-century Persia, also teaches the oneness of God. It maintains that the world’s major religions share a common divine origin and that their founders brought revelations suited to different periods of human history. The oneness of God, the unity of religions, and the unity of humanity are three essential principles of this tradition.
Yazidism, a religion originating in the Middle East, likewise recognizes one God, the creator of the universe. In this tradition, God entrusted the governance of the world to seven holy beings, the foremost of whom is Tawûsê Melek, the Peacock Angel. These beings are not regarded as competing gods.
Zoroastrianism, an ancient Iranian religion, places Ahura Mazda, the supreme divinity associated with wisdom and goodness, at the center of its beliefs. However, its classification as a monotheistic religion remains a matter of debate, particularly because of the important role played by the opposition between the forces of good and evil.
The boundary between monotheism and polytheism is not always as straightforward as it might appear. Some traditions within Hinduism recognize a supreme divine reality of which several deities may be understood as manifestations. Others give particular prominence to one deity without necessarily denying the existence of others.
Historians of religion also use the concepts of monolatry and henotheism. Monolatry refers to the exclusive worship of one deity without necessarily denying the existence of other gods. Henotheism generally describes a form of belief in which one deity occupies a superior position without entirely excluding others.
These distinctions are important for understanding the historical emergence of monotheistic religions. Scholars generally consider that religious beliefs developed gradually, sometimes from traditions in which several deities were recognized. The history of ancient monotheism remains an area of ongoing research and debate, as explained by the Stanford Encyclopedia of Philosophy.
Finally, monotheism should not be confused with deism, which accepts the existence of a creator God without necessarily recognizing divine revelation, or with pantheism, which identifies the divine with the whole of reality.
Monotheism therefore refers primarily to a conception of divine oneness, rather than to any particular religion. This belief can be accompanied by very different doctrines, practices, and traditions. It represents one of the major religious frameworks through which human societies have sought to understand the origin of the world, the nature of the divine, and humanity’s place in the universe.