Ontological reductionism is the idea that everything that exists is made from a small number of basic substances that behave in regular ways. Compare to monism.

Ontological reductionism is evident in the dominant discourses in the business of commercial and academic study of the management of software development. This provides an illustration of how ontological reductionism is often present as an unquestioned pre-understanding by members of these communities.

As an example consider the use of the term "process" as it is commonly used to describe the of development of software products. Here a "process" is used as a representation of a system of transformation applied to defined inputs and which produces defined outputs. Defined inputs are transformed through a process to produce a defined output. At its simplest conception a process is an open-ended input/output system similar to or equivalent to algorithmic functions in mathematics and physics. This use is clearly described when reading either ISO 9001:2000 or ISO/IEC 12207 and conveys the unsubstantiated and unchallenged assumption that a process is a separable standalone unit of work, production or product transformation. Further a "process" is assumed to be coupleable such that the outputs of one process can be coupled to the input of another process. In this way separate ontologically reduced atomic processes can be coupled, joined or grouped together to create a larger system of processes which may in turn be represented as a higher-level process.