Among jurists and law philosophers is today diffused an attitude of general disillusionment towards certainty-predictability of law, sometimes referred to as a dinosaur, if not a chimera, of the juridical philosophy. Many skeptical authors easily showed that the creative element of every “application” of law does hinder every chance of an exact prediction of the legal consequences of facts and behaviours. With the analytical re-construction of a dispositional and non classificatory concept of certainty-predictability, this work tries to avoid this and other problems, proposing, in the meanwhile, a return to the original ratio of the concept itself: the functionality of predictions towards the goals of individual actions, with particular attention to the possibility to plan our own lives in a legally aware and informed way.