Explanandum and explanans


An explanandum is a sentence describing a phenomenon that is to be explained, and the explanans are the sentences adduced as explanations of that phenomenon. For example, one person may pose an explanandum by asking "Why is there smoke?", and another may provide an explanans by responding "Because there is a fire". In this example, "smoke" is the explanandum, and "fire" is the explanans.

In scientific method

and Paul Oppenheim, in their deductive-nomological model of scientific explanation, motivated the distinction between explanans and explanandum in order to answer why-questions, rather than simply what-questions:
Specifically, they define the concepts as follows:
The crucial comment, with respect to the scientific method, is given as follows:

In biological systematics

Philosopher of science Ronald Brady proposed that the pattern of relationships among organisms represents an explanandum that is prior to and independent of its explanation, the theory of evolution. This is an expression of the pattern cladistic viewpoint.

In the Social Sciences

wrote: "I argue that all explanation is causal. To explain a phenomenon is to cite an earlier phenomenon that caused it."

Related terms