The need to represent the world, classify things and reason about categories appeared right at the beginning of human reasoning. The first and most famous philosopher to analyse systematically the representation of the world, and whose works have come down to us, was without doubt Aristotle, the "master of those who know" in the words of the world-famous Italian poet Dante Alighieri. Philosophers analysed the subject much further, to understand and hypothesise on essence and attributes, on categorisation, on the relationships between categories and on reasoning about known experience to obtain more information. Certainly they would never have imagined that such basic reasoning and cerebration, which was then aimed at the human understanding of the world, would later become the foundation of information science, and even robotics.

Current research directions in robotics are aimed at robots that are ever more conscious and capable. An essential ability, not only in itself but also for completing complex tasks, is certainly the robot's ability to represent the world, categorise it and reason about known experience of the world in order to obtain more information. The lecture presents the basic concepts of ontology, their current use in robotics, and recent developments towards probabilistic ontologies for representing the robot's uncertainty (and various degrees of uncertainty) about the world and the development of the world.

The lecture will also refer to several projects in which the author is involved, with financial support from EU sources and the British and Canadian ministries of defence.