We introduce a new theory of concepts conceived as structured abstract entities. The theory is based on the key notion of Transparent Intensional Logic (TIL), known as TIL construction. The rich procedural semantics of TIL makes it possible to explicitly analyze all the semantically salient features of natural language expressions. We illustrate how to make use of TIL theory of concepts in distinguishing analytical and empirical concepts, and particular kinds of necessities. We also deal with a rigorous specification of requisite relations between intensions such as properties. Finally, ontology is characterised as a relatively stable part of the system that should play an integrating role. We show how to make use of TIL rich theory in specification of the content of ontologies in a multi-agent system.