In addition to rule interaction issues, another research focus of the Mikrokosmos project is the integration of two approaches to lexical semantics that are usually considered to be incompatible. The approach to lexical semantics taken by researchers in syntactic theory is useful for identifying predicate-argument relations in syntactic structure, but is not suitable as the basis of an interlingua for machine translation. We explain the reason why in the talk. On the other hand, an approach to lexical semantics driven by ontological issues provides a good basis for an interlingua, but is non-optimal as a basis for identifing predicates and their arguments in particular languages. In this talk, we describe how the two approaches to lexical semantics are integrated in the Mikrokosmos lexicon.