Gerd Gigerenzer challenges the notion that many "errors" in probabilistic reasoning, such as overconfidence bias, conjunction fallacy, and base-rate neglect, are violations of probability theory. He argues that these "errors" are often the result of a narrow normative view that ignores fundamental conceptual distinctions in probability theory, such as single case versus relative frequency. By recognizing and using these distinctions, Gigerenzer suggests that what appear to be stable "errors" can disappear, reappear, or even invert. He provides examples from overconfidence bias, conjunction fallacy, and base-rate neglect to illustrate how rephrasing problems in a frequentist or Bayesian framework can transform judgments and make "cognitive illusions" disappear. Gigerenzer also discusses the concept of heuristics, arguing that the term has been misused in the "heuristics and biases" literature to explain "errors" rather than to describe adaptive strategies. He concludes by suggesting a revised understanding of judgment under uncertainty that is more aligned with the probabilistic revolution.Gerd Gigerenzer challenges the notion that many "errors" in probabilistic reasoning, such as overconfidence bias, conjunction fallacy, and base-rate neglect, are violations of probability theory. He argues that these "errors" are often the result of a narrow normative view that ignores fundamental conceptual distinctions in probability theory, such as single case versus relative frequency. By recognizing and using these distinctions, Gigerenzer suggests that what appear to be stable "errors" can disappear, reappear, or even invert. He provides examples from overconfidence bias, conjunction fallacy, and base-rate neglect to illustrate how rephrasing problems in a frequentist or Bayesian framework can transform judgments and make "cognitive illusions" disappear. Gigerenzer also discusses the concept of heuristics, arguing that the term has been misused in the "heuristics and biases" literature to explain "errors" rather than to describe adaptive strategies. He concludes by suggesting a revised understanding of judgment under uncertainty that is more aligned with the probabilistic revolution.