Slothful induction, also known as the a priori fallacy, is the failure or refusal to see or concede the most likely inference from the evidence. The failure to infer is rarely due to sloth. It demonstrates an unwillingness to follow the evidence wherever it may lead due to stupidity, dogma, or vested interests. Usually it is a red flag that someone is not principally interested in the truth of a matter. And, because inductive arguments are at best probabilistic, someone can always hold out against the preponderance of evidence. Nevertheless, there are times when it is appropriate to resist the inference of even a good inductive argument, namely, when there are countervailing reasons that support the contrary conclusion. For example, when new evidence appears against a well-established scientific theory, it can be appropriate to retain the current theory until the evidence to the contrary is sufficiently strong. In such cases an ad hoc hypothesis may be introduced to explain how the established thesis may still be true in spite of the implications of this new inductive evidence.
The second fitness-enhancing cognitive capacity is the tendency to recognize that things that are similar to each other with respect to their observed properties are likely to be similar with respect to their unobserved properties… This capacity is advantageous because the principle it is centered around is true, and failure to reason in accordance with the principle can be deadly. Failure to infer that these round, shiny, bright berries are likely to be poisonous from the fact that those other round, shiny, bright red berries produced frothing at the mouth and then death in one’s companion yesterday may well lead to trouble for oneself today.
