I am using the term &quot;ontology&quot; to mean &quot;a description of truth&quot;, and &quot;epistemology&quot; to mean &quot;how do we know what truth is&quot;. Of course, these are philosophical definitions, which (as the article says) are not necessarily that applicable.<p>The article in question uses OWL -- which is a subset of first order logic -- to illustrate the point. Clojure is (in this article) just a syntactic wrapping.