Professional studies on the role of the librarian have been developed around six axis. Amongst these, one notes the predominance of applied research. However, French production in this area remains poor. Using as an example the field of collection policies, the author of the article questions the possibility of building problematical theories to influence relevant applied research, under the form of "action research" in particular, and on the place of research in professional activity. He suggests that the very process of library activity should be questioned and that researchers from all horizons should be involved.