How to evaluate the rationality of heuristics?

One of the most debated topics among those who study heuristics is the question of their rationality. The present paper proposes an answer to this question based on the ideas of instrumental rationality and the probabilistic nature of heuristic judgments and decisions. Accordingly, it is argued that the rationality of heuristics is determined by their effectiveness, i.e., their ability to achieve a desired result. At the same time, heuristics do not always produce such a result, but only in a certain number of cases. Therefore, their effectiveness should not be evaluated by the binary logic criterion (effective/ineffective) but by the probabilistic criterion, i.e., by how often they lead to the desired result. Each heuristic has a certain objective probability of achieving such a result, which determines its rationality. However, this probability is mostly unknown to us, so when relying on heuristics, we are likely guided by a subjective perception of it, which serves as a metacognitive cue about the probability of the conclusion obtained with the help of this heuristic.