Theism is broadly defined as the belief in the existence of the Supreme Being or deities. In common parlance, or when contrasted with deism, the term often describes the classical conception of God that is found in monotheism (also referred to as classical theism) or gods found in polytheistic religions—a belief in God or in gods without the rejection of revelation as is characteristic of deism.
Atheism is commonly understood as rejection of theism in the broadest sense of theism, i.e. the rejection of belief in God or gods. The claim that the existence of any deity is unknown or unknowable is agnosticism.
Ietsism (Dutch – "somethingism") is an unspecified belief in an undetermined transcendent reality. It is a Dutch term for a range of beliefs held by people who, on the one hand, inwardly suspect – or indeed believe – that "there must be something undefined beyond the mundane and that which can be known or can be proven", but on the other hand do not necessarily accept or subscribe to the established belief system, dogma or view of the nature of a Deity offered by any particular religion. Some of the English language related terms are agnostic theism (though very many ietsists do not believe in one or more gods and are thus atheists), eclecticism, deism and spiritual but not religious. Ietsists might call themselves Christian or followers of an other religion based on cultural identification with that religion, without believing in the dogmas of that particular religion.
