Research News: While aids to synthesis design are available to the organic chemist, for example the Woodward-Hoffmann rules, the situation for the chemist involved in solid-state synthesis is somewhat different. Here, the researcher is forced into planning synthetic steps in a much more rudimenatry way. In this, somewhat extended article, a new concept for the design of solid-state syntheses, based on improved descriptions for acidity, basicity, electrophilicity, and nucleophilicity in the solid state, is presented.