Is there beauty in ontologies?

This position paper presents an introduction to the special issue of Applied Ontology on "Beautiful Ontologies". It discusses the relevance of considering the notion of beauty when building and evaluating ontologies, making a parallel with other disciplines such as physics and software engineering. It also discusses the difference between the beauty of an ontology and the notion of quality generally considered in ontology evaluation. Finally, it discusses examples included in the articles of the special issue, to show that a beautiful ontology can be seen as one that integrates contradictory requirements.