 The trial and error procedures adopted by firms to improve along a technological trajectory (S.F.2) have taken Dosi to assess the issue of uncertainty.At a general level, trial and error procedures imply that firms might not be able to forecast completely the outcome of a choice they make; in fact, if they could foresee the error, they would presumably avoid it because it is costly.Such a fact is strongly at odds with any assumption of "perfect rationality" or "farsightedness" on the side of economic agents, which is a foundational element of the Neoclassical approach.