monotheism, belief in the existence of one god, or in the oneness of God; as such, it is distinguished from polytheism, the belief in the existence of many gods, and from atheism, the belief that there is no god. Monotheism characterizes the traditions of Judaism, Christianity, and Islam, and elements of the belief are discernible in numerous other religions.
Monotheism and polytheism are often thought of in rather simple terms—e.g., as a merely numerical contrast between the one and the many. The history of religions, however, indicates many phenomena and concepts that should warn against oversimplification in this matter. There is no valid reason to assume, for example, that monotheism is a later development in the history of religions than polytheism. There exists no historical material to prove that one system of belief is older than the other, although many scholars hold that monotheism is a higher form of religion and therefore must be a later development, assuming that what is higher came later. Moreover, it is not the oneness of god that counts in monotheism but his uniqueness; one god is not affirmed as the logical opposite of many gods but as an expression of divine might and power.
The choice of either monotheism or polytheism, however, leads to problems, because neither can give a satisfactory answer to all questions that may reasonably be put. The weakness of polytheism is especially revealed in the realm of questions about the ultimate origin of things, whereas monotheism runs into difficulties in trying to answer the question concerning the origin of evil in a universe under the government of one god. There remains always an antithesis between the multiplicity of forms of the divine manifestations and the unity that can be thought or posited behind them. The one and the many form no static contradistinction; there is, rather, a polarity and a dialectic tension between them. The history of religions shows various efforts to combine unity and multiplicity in the conception of the divine. Because Christianity is a monotheistic religion, the monotheistic conception of the divine has assumed for Western culture the value of a self-evident axiom. This unquestioned assumption becomes clear when it is realized that for Western culture there is no longer an acceptable choice between monotheism and polytheism but only a choice between monotheism and atheism.