Structuralism’s basic ontological assumptions are as follows:

(1) There are scientific theories (in at least three different senses of the term ‘theory’).

(2) Scientific theories are cultural objects of a rather abstract kind in the sense that they are not spatiotemporally localized the way macroscopic physical objects are. Their ontological status is similar to that of other abstract cultural objects like languages [..], symphonies, computer programs, and the like.

(3) In a way similar to other abstract cultural objects, scientific theories have a ‘deep structure’. This means that their identity criteria and essential components cannot be detected in a straightforward manner by just ‘looking at’ the surface appearance of the concrete objects (e.g scientific texts) instantiating them. To display them is a non-trivial task.

(4) Scientific theories are genidentical entities. They have a ‘life’ of their own, like persons or nations do.

(5) Scientific theories are not ‘monads’. They are essentially related to things outside themselves. At least part of this outside world consists of other scientific theories. This means that there are intertheoretical relations and that they belong to the ‘essence’ of scientific theories.

As for structuralism’s specific methodology, it its choice is, in part, prompted by the previous ontological assumptions.

(6) The best way to reveal the deep structure of a scientific theory as an abstract entity is by means of formal analysis. As far as possible, formal techniques of analysis and reconstruction should be preferred to explications in ordinary language. […]

(7) More specifically, given the kind of conceptual analysis required by structuralism, the most adequate formal tool, because of its universal character, appears to be set theory. […]