The paper starts from the assumption that expert thinking is a complex manner of thinking of higher order, comprising higher mental functions and complex capabilities based on deep structures and knowledge patterns. It is a domain-determined and specialized thinking developed through systematic education. Particular aspects of ability, selected for this study, primarily concern the relation between abilities and knowledge and the relation between general and specific abilities. Particular emphasis was laid on the key concepts of the theories presented, relevant for the study of the complex nature of expert thinking. Special attention was paid to mediated intelligence and the process of systemogenesis of knowledge, Katel’s definition of crystallized intelligence, Gardener’s work on multiple intelligences in the context of knowledge and experience as well as Sternberg’s two-facet subtheory. The capability for abstract thought and the ability to select what is important as well as the domain of relevant specific capability are assumed to be of special relevance for understanding expert thinking and, as such, they were articulated and examined. Expert thinking-abstract, specialized and domain-specific, seems to be based on general and specific capabilities and their interaction.