Proof theory and semantics of an adaptive logic that deals adequately with change in individuals with or without a name are presented. New logical constants are introduced, viz. indicators. Within a given context they function as names, predicates and quantifiers at the same time. The thus extended language (of classical logic) has a big expressive power and solvespartly-the (classical) non-logical presuppositions with respect to 'the existence of individuals'. Nevertheless, from a purely

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... l point of view, the here presented logic requires nothing but a very intuitive selection of classical models of the premises, viz. the minimally abnormal ones. 1 This notational change is so simple that from my point of view it is amazing that Russell and Whitehead did not use it in their [9] .