Ontology deals with questions concerning what entities exist or can be said to exist.
Proposed rule: An ontological definition of affordances cannot include, in full or in part, a relationship between two entities, if we wish to adhere to a realist account of said concept.
Reason: Relationships imply mono-dependence or co-dependence.
Reasoning: An ontological definition of a concept including a relationship, implicates ‘mono- or co-dependence’ with ‘what exists’.
Premise A1: If either entity is dependent on the other, and
Premise A2: dependence is required for existence,
Conclusion A: then, there will be situations where either will not exist.
Premise B1: If both entities are dependent on each other, and
Premise B2: dependence is required for existence,
Conclusion B: then there will be situations where neither will exist.
Consequence: If affordances are in full or in part defined ontologically as a relationship, then affordances will align itself with idealism, since we will have situations where one or both entities do not exist.