We view the content of ontology via a logic of intensions. This is due to the fact that particular intensions like properties, roles, attributes and propositions can stand in mutual necessary relations which should be registered in the ontology of a given domain, unlike some contingent facts. The latter are a subject of updates and are stored in a knowledge-base state. Thus we examine (higher-order) properties of intensions like being necessarily reflexive, irreflexive, symmetric, anti-symmetric, transitive, etc., mutual relations between intensions like being incompatible, being a requisite, being complementary, and so like. We also define two kinds of entailment relation between propositions, viz. mere entailment and presupposition. Finally, we show that higher-order properties of propositions trigger necessary integrity constraints that should also be included in the ontology. As the logic of intensions we vote for Transparent Intensional Logic (TIL), because TIL framework is smoothly applicable to all three kinds of context, viz. extensional context of individuals, numbers and functions-in-extension (mappings), intensional context of properties, roles, attributes and propositions, and finally hyper-intensional context of procedures producing intensional and extensional entities as their products.