I have always said that a belief was knowledge if it was (1)true, (2)certain, (3)obtained by a reliable process. But the word 'process' is very unsatisfactory; we can call inference a process, but even then unreliable seems to refer only to a fallacious method not to a false premiss as it is supposed to do. Can we say that a memory is obtained by a reliable process? I think perhaps we can if we mean the causal process connecting what happens with my remembering it. We might then say, a belief obtained by a reliable process must be caused by what are not beliefs in a way or with accompaniments that can be more or less relid on to give true beliefs, and if in this train of causation occur other intermediary beliefs these must all be true ones.
E.g. 'Is telepathy knowledge?' may mean : (a) Taking it there is a process, can it be relied on to create true beliefs in the telepathee (within some limits, e.g. when what is believed is about the telepathee's thoughts)? or (b) Supposing we are agnostic, does the feeling of being telepathed to guarantee truth? Ditto for female intuition, impressions of character, etc. Perhaps we should say not (3)obtained by a reliable process, but (3)formed in a releable way.
We say 'I know', however, whenever we are certain, without reflecting on reliability. But if we did reflect then we should remain certain if, and only if, we thoght our way reliable. (Supposing us to know it ; if not, taking it merely as described it would be the same, e.g. God put it into my mind : a supposedly reliable process.) For to think the way reliable is simply to formulate in a variable hypothetical the habit of following the way.
One more thing. Russell says in his Problems of Philosophy that there is no doubt that we are sometimes mistaken, so that all our knowledge is infected with some degree of doubt. Moore used to deny this, saying of course it was self-contradictory, which is mere pedantry and ignoration of the kind of knowledge meant.
But substantially the point is this : we cannnot without sefl-contradiction say p and q and r ... and one of p, q, r are then infected with doubt. But Moore is right in saying that not necessarily all are so infected ; but if we exempt some, we shall probably become fairly clear that one of the exempted is probably wrong, and so on.

In: Ramsey, Frank Plumpton: Philosophical Papers (ed. by D.H.Mellor). Cambridge 1990, pp.110-111