The effects of innovation are usually multi-sectoral and trespass theoretically constituted borders between spheres and fields, which explains why there are multi-disciplinary approaches to innovation. Literature on innovation can be found in research in economics, public administration, management studies, political science, law, sociology and technology studies. Various conceptual perspectives on innovation are one of the results. Increased social innovativeness is marked by a more frequent (overall or within the social innovation process) and more substantial (clearly recognisable or dominant) and more sustainable (lasting) involvement in the development of such solutions. As regards the question who such actors are and where we can find them we have developed one main hypothesis: Social innovativeness varies by organisational form and actor involvement in the sense that the properties of third sector organisations and volunteering make its formation particularly likely.