I respectfully suggest that it is time to set ego aside, let go of what I, the individual, knows, and instead focus on what we, the collective, know. I as an individual am limited by the biological hardware I was born with, which in turn can be limited by injury, pathology, and instinctual behaviors. Additionally, what I know as an individual is heavily biased and constrained by socialization and many other psychological factors. Therefore, instead of focusing our attention on the limited and constrained observations of one individual, we look at all the billions of observations of billions of individuals throughout history. By comparing and analyzing these many observations, we are able to gauge the strength and value of shared observations. This is how we know what we know. It does not completely solve the issues that constrain the individual observer, but it does mitigate them. To what extent it helps to overcome our individual limitations and provide a true picture of reality, only time will tell.
So to the question at hand “Must we be absolutely certain that a true belief is justified before we can legitimately call our true belief 'knowledge'?”, it is clear that any justification for a personally held belief needs to be supported by our collective knowledge to be of any value, and as alluded to in other posts, even then we cannot be 100% sure that we are collectively “getting it right”. That is why we must constantly reevaluate and reanalyze what we know, especially in light of new and corroborated observation.
