Ietsism (Dutch: ietsisme (pronounced [itsˈɪsmə]) – "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. In terms of statistics this might influence outcomes when people are asked about their religion or beliefs without more in-depth interviewing.
In some Eastern European censuses (Albanian, for example), those having ietsistic beliefs are counted as believers without religion.
The name derives from the Dutch equivalent of the question: "Do you believe in the conventional 'Christian' God?", a typical ietsist answer being "No, but there must be something", "something" being iets in Dutch.
The atheist political columnist and molecular biologist Ronald Plasterk (who later served as the Dutch Minister of Education, Culture and Science and Minister of the Interior and Kingdom Relations) published a piece in 1997 in the magazine Intermediar in which he used the word. The term became widely known in the Netherlands after Plasterk used it in a feature for the television programme Buitenhof. In October 2005, the word ietsisme was included in the 14th edition of the Dutch Language Dictionary Dikke Van Dale.