 The table below illustrates these distinctions in the New Riddle of Induction and the Raven example. Genin and Kelly investigate the principle that inductive methods should minimize the number of regressive mind changes, that is, the number of times new evidence leads the method to abandon a true hypothesis in favor of a false one. The notion that regressive mind changes are a mark of epistemic failure matches a long tradition in epistemology.  Defeasibility theories of knowledge (see the link in the Other Internet Resources section below)  hold that in order for an agent’s true belief to count as knowledge, it must be indefeasible in the sense that accepting further propositions should not lead the agent to abanon her belief. Translated into the language of mind changes, this means that an inquirer’s true current conjecture can count as knowledge only if there is no further evidence that would lead her to change her mind and adopt an alternative false conjecture.  Plato’s Meno  conveys this point vividly. 