 We still need to qualify the entailment in some way to circumvent the problem discussed earlier. Whenever I have any justification at all for believing a proposition that turns out to be necessarily true, that justification will entail the necessary truth. But we do not want just any sort of justification to yield infallibly justified belief, even if the object of that belief is a necessary truth. This problem is notoriously difficult to solve (see the entry on  Certainty  for more), but intuitively the solution should have something to do with the relation between the fact that would make true the proposition entailed and the fact that would make true the proposition that entails it. More specifically, we could say that P entails* Q only if the fact that would make P true is at least a constituent of the fact that would make Q true. This suggestion can be considered at best only preliminary since we will obviously need a more detailed account of facts and their constituents. That I have grey hair entails that someone has grey hair, but is my having grey hair a constituent of the fact that is someone’s having grey hair? There is certainly a sense in which it is something one can point to in answer to the question “What makes it true that someone has grey hair?” One cannot appropriately point to my having grey hair as something that makes it true that two plus two equals four. With some such relation in place, perhaps we can appropriately restrict the class of necessary truths we can be infallibly justified in believing, and still allow contingent truths to be infallibly justified: there is a sense in which one can “point” to one’s own experience when asked, “What makes it true that you are in pain?”