Internalists argue that a justification a thinker cannot access from the inside cannot be doing any justifying work for that thinker; externalists reply that small children and animals plainly have justified perceptual beliefs despite being unable to reflect on their own reliability. Neither side has produced a case the other accepts as decisive.
What would resolve this A shared account of what justification is FOR, whether it is about the thinker's own responsible believing or about tracking truth, would settle which condition is required; the two camps currently start from different accounts of that point.
OpenEpistemologyStanford Encyclopedia of Philosophy