It is increasingly evident that there is more to biological evolution than natural selection; moreover, the concept of evolution is not limited to biology. We propose an integrative framework for characterising how entities evolve, in which evolution is viewed as a process of context-driven actualisation of potential (CAP). Processes of change differ according to the degree of non-determinism, and the degree to which they are sensitive to, internalise and depend upon a particular context. The approach enables us to embed phenomena across disciplines into a broad conceptual framework. We give examples of insights into physics, biology, culture and cognition that derive from this unifying framework.

Purpose - To develop a theory of concepts that solves the combination problem, i.e. to deliver a description of the combination of concepts. We also investigate the so-called "pet fish problem" in concept research.

Design/methodology/approach - The set of contexts and properties of a concept are embedded in the complex Hilbert space of quantum mechanics. States are unit vectors or density operators and context and properties are orthogonal projections.

Findings - The way calculations are done in Hilbert space makes it possible to model how context influences the state of a concept. Moreover, a solution to the combination problem is proposed. Using the tensor product, a natural product in Hilbert space mathematics, a procedure for describing combined concepts is elaborated. This procedure also provides a solution to the pet-fish problem, and it allows the modeling of an arbitrary number of combined concepts. By way of example, a model for a simple sentence containing a subject, a predicate and an object, is presented.

Originality/value - The combination problem is considered to be one of the crucial unsolved problems in concept research. Also the pet-fish problem has not been solved by earlier attempts of modeling.

Purpose - To elaborate a theory for modeling concepts that incorporates how a context influences the typicality of a single exemplar and the applicability of a single property of a concept. To investigate the structure of the sets of contexts and properties.

Design/methodology/approach - The effect of context on the typicality of an exemplar and the applicability of a property is accounted for by introducing the notion of "state of a concept", and making use of the state-context-property formalism (SCOP), a generalization of the quantum formalism, whose basic notions are states, contexts and properties.

Findings - The paper proves that the set of context and the set of properties of a concept is a complete orthocomplemented lattice, i.e. a set with a partial order relation, such that for each subset there exists a greatest lower bound and a least upper bound, and such that for each element there exists an orthocomplement. This structure describes the "and", "or", and "not", respectively for contexts and properties. It shows that the context lattice as well as the property lattice are non-classical, i.e. quantum-like, lattices.

Originality/value - Although the effect of context on concepts is widely acknowledged, formal mathematical structures of theories that incorporate this effect have not been successful. The study of this formal structure is a preparation for the elaboration of a theory of concepts that allows the description of the combination of concepts.