The Project Halo (www.projecthalo.com) has the long term objective of developing a Digital Aristotle, i.e. a knowledge system that is able to answer questions in a particular domain and give explanations for its answers. In this paper we report about the Ontoprise contribution to the Halo Pilot Project, in which various competing ontology engineering methodologies and knowledge system capabilities have been investigated. Concerning the first, we describe how we dealt with engineering a significant set of laws from chemistry that we had to let interact at different levels of generality and in varying orders. With regard to the latter, we report on the ability of our system to produce coherent and concise explanations of its reasoning. The importance of these two aspects can hardly be underestimated in the Semantic Web, as with future growth the interaction of large sets of laws will require dedicated management as well as the ability to let the user explore the trustworthiness of the ontology and the underlying data sources.