The article first presents the characteristics of the national research evaluation systems of some countries, in order to show the big difference that exists at the level of the political objectives and in terms of the methodological choices. Then proceed to offer a "formal theory" of evolution of national systems of evaluation, based on the idea of the inherent limitations of the two main methods of assessment. The authors tries to corroborate this idea by presenting the most significant results of the research on peer review and bibliometrics. The confirmation of the inherent limitations of the methodologies available (and their mix) will take the authors, in conclusion, to poin out the limit of the Italian system of assessment, not so much in terms of methodology as a political aspect, thus showing to a re-orientation of the debate in this direction.
Keywords: Research Evaluation; National System for Research Evaluation; Peer Review; Bibliometrics.