Design is materialized philosophy.
When designing something — which always and necessarily means designing something for someone — the central question is always: what is the right philosophy for this context?
The purpose of design research is to get to the heart of this central question out, and then to pose the design problem in such a way that designers think about the design problem in the right way, from the philosophical perspective suited to the problem.
Design briefs are tiny philosophical primers.
A good design brief will effect a perspectival shift in the reader (the designer) that brings new possibilities into view, possibilities that were entirely inconceivable prior to the shift. This phenomenon is what is commonly called inspiration.
Design researchers are in the precision inspiration business.