There have been a growing number of publications suggesting that philosophical ontologies will define a rigorous basis for conceptual modelling, particularly for data modelling methods and notations. An examination of an underlying psychological assumption of the conceptual modelling process is used to show that philosophical ontologies are being used as a ‘telescope’ to view the products of yet another ‘telescope’ and this undermines their reliability by being too far removed from the actual modelling process. An ontology of conceptual structure, derived through linguistic analysis provides a psychologically realistic alternative to the philosophical ontologies that is as close to its mental interpretation as possible and is a more promising approach to understanding the modelling process.