In line with the underlying roots of the phenomenon, I regard a think tank as „any open organisation built around a permanent cadre of researchers, whose mission it is to develop, on an objective basis, 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 which allows us to examine real institutions which are considered, or which 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. For openness implies debate with the outside world. Naturally, openness can be achieved to a greater or lesser extent.