Since it is only five years since the publication of our paper, "Geographical categories: An ontological investigation" (Smith and Mark 2001), it seems somewhat
strange to be making retrospective comments on the piece. Nevertheless, the field
is moving quickly, and much has happened since the article appeared. A large number
of papers have already cited the work, which suggests that there is a seam here that
people find worthy of being mined. In this short essay, we first review the paper and attempt to assess its significance from the perspective of our current work. We then put the paper in the context of our individual and joint works, which led up to it, and summarize our research trajectories since the paper appeared, pointing out what some of this reveals about spatial ontology in general. We conclude with some remarks on the future of ontological research in geographical information science.