I argue why I think that Computer Science (or better: Informatics) is a "natural science", in the same sense that physics, astronomy, biology, psychology and sociology are a natural science: they study a part of the world around us. In that same sense, I think Informatics studies a part of the world around us. For a similar talk (including script), but more aimed at a Semantic Web audience in particular, see http://www.cs.vu.nl/~frankh/spool/ISWC2011Keynote/ (or http://videolectures.net/iswc2011_van_harmelen_universal/ for a video registration)