I was reading the IEP's article on epistemic justification, and came across the following paragraph(s):
https://iep.utm.edu/epi-just/#SH1a
I'm having a hard time with the sentence "Proposition 3 is not justified unless Propositions 1 and 2 are justified." Why is this true? If we accept the rule "After a person sees that X, they are justified in believing X," then I am justified in believing (3), regardless of whether I am justified in believing (1) and (2). In other words, if some set of facts makes me justified in believing (3), why must these facts take the form "I am justified in believing..."?
I have come to the following, slightly strange understanding which may well need correction. When a person sees the cat on the mat, they are justified in believing there is a cat on the mat. When a person tries to justify their belief that they are justified in believing there is a cat on the mat, they must justify their belief in the set of facts which would imply they are justified in believing there is a cat on the mat. It is while doing this that they must justify (1) and (2). On this interpretation, "I am justified in believing (3)" only requires "I see a cat on the mat". The claim "I am justified in believing that I am justified in believing (3)" requires "I am justified in believing (1) and (2)".
Edit: A commenter has pointed out that one can be justified in believing something false, and unjustified in believing something true, so that a claim being true and its being justified are logically independent. This is exactly the reason why I'm confused. The facts about S which make S justified in believing (3) could be facts like "S sees a cat on the mat," instead of "S is justified in believing S sees a cat on the mat." In this case, whether or not S is justified in believing that S sees a cat on the mat is immaterial. S is under no obligation to show that S is justified in believing S sees a cat on the mat; S has an obligation to show that S sees a cat is on the mat.