The practical explication suggests that all attempts to state necessary and sufficient conditions for knowledge will either produce a set of conditions that is insufficient, or will achieve sufficiency only by including conditions too strong to be necessary. This is illustrated with respect to the JTB (justified true belief) analysis, reliabilism, the causal theory, and the NFL (no false lemmas) principle. For the first three, it is always possible to think of circumstances such that, even though the subject reached the belief p by the required means, she was right against all the odds, given those further circumstances. And if justification (or some other condition) is stipulated to entail the truth of p, then this imposes an impossibly strong condition or serves merely to reiterate the famous first condition for knowledge. As for NFL, this calls for a near-omniscience on the inquirer's part, so that it is too strong to be a necessary condition for knowledge.
Keywords: causal theory, conditions for knowledge, justification, knowledge, reliabilism, true belief