In line with the underlying roots of the phenomenon, I regard a think tank as any open organization built around a permanent cadre of researchers or experts, whose mission it is to develop, on an objective basis, syntheses and ideas relevant to policy-making or the formulation of private or public strategies, subscribing to a perspective of public interest. Clearly, this is a radical and, therefore, idealistic definition, but one that allows us to examine real institutions that are considered, or consider themselves, as think tanks.

The criterion of openness to the public is an essential distinction between contemporary think tanks and advisors to heads of non- democratic states, either of times gone by (such as the secret cabinet of Louis XV), or of today. Openness implies debate with the outside world. Naturally, openness can be achieved to a greater or lesser extent.