I have been told that knowledge is usually analyzed as being justified true belief (although this conception has been criticized - namely after Gettier published his famous article - it seems to be widely accepted, at least as a good approximation of what knowledge really is). However, I don't see why the truth condition is necessary. Indeed, by definition, we can only evaluate the truth value of a proposition by making appeal to our justification for this proposition. Moreover, believing some proposition is believing this proposition to be true. When I say "I know x", it seems therefore to me that I don't say anything else than "I believe x and I am justified in believing x", with the truth condition of the tripartite definition of knowledge encompassed by the belief and justification conditions. Can someone explain me then why knowledge is not defined as just "justified belief" ? Many thanks in advance.