This restriction appropriately limits which necessary truths can be infallibly justified while still permitting infallible justification of contingent truths.

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 intuiti