When there are conflicts of observation, when experiments cannot be replicated, scientists may then retreat to a study of the various specific observations so as to explain the conflict, in the course of which they would make use of the concept of observation, or of some specification of that concept.
Ernest SosaPhilosophers do need to have intuitions of various specific sorts: ethical, metaphysical, etc., depending on their targeted subject matter. And they must make intuition reports, as they record the contents of their intuitions. But they need not go into whether an intuition has been enjoyed.
Ernest SosaIn arriving at the relevant theory about the specifics of our faculty of vision we will presumably use our eyes to gather relevant data. Based on such data we come to know about the optic nerve, the structure of our eyes, the rods and cones, etc., so as to explain how it is that vision gives us reliable access to the shapes and colors of objects around us. In reliably arriving at that theory we thus exercise the very faculty whose reliability is explained by the theory. There is no vice in this sort of circularity.
Ernest Sosa