The thesis formulates a contribution to a general theory of design that aims at identifying concepts common to large number of design domains.After the analysis of the state of the art, the thesis formulates a conceptual framework as well as an in-depth analysis of following concepts: project, artefact, design space, design process, design organisation and the cognitive processes at the level of the designer. A case study provides an illustration of the different concepts. The conclusion highlights the added value and the limits of the contribution.