The discipline of program evaluation has invested more energy in developing methodologies during the past twenty years than to understand certain strategic stakes such as the evaluative reasoning which supports the practice. Some authors, to cite only Fournier and Scriven, are particularly interested by the influence of evaluative reasoning on conclusions and justifications but, so far, these concerns do not seem to have aroused much interest. This fact is all the more surprising given that the transition from the description stage to one of judgment constitutes the cornerstone of any good-quality program evaluation. It is from this point of view that this article approaches the question of the reasoning underlying any evaluative process. More precisely, the author studies the way in which evaluators produce and justify their judgment.