 Wolff’s system is also structured according to a notion of rational order. The “order of science” pertains to the relationship not only between individual sciences but also between the sets of discoverable facts within each given discipline (cf. DP: §§132–5). The central idea here is that certain truths are known prior to, and serve as a basis for discovering, other truths. And just as there are certain facts that are more fundamental and serve as a basis for discovering other facts, there are, Wolff believes, certain sciences whose subject matter is more basic and which ultimately stand as the foundation for other sciences that have a more specialized focus. For example, in the “order of demonstration”, physics follows general cosmology which, in turn, follows ontology (or first philosophy) (DP: §§94–5).