true belief vs knowledge

A true belief counts as knowledge only if it is justified. For example, your belief that a horse will win the race may turn out to be true but it is not knowledge unless it is well-based rather than, say, a fortunate guess.

We conjecture that reference-determining belief as knowledge because of an implicit assumption that permeates their thinking about semantics, "the Cartesian assumption" that a speaker's competence in using an expression that amounts to (tacit) knowledge about its meaning; the competence involves a non-empirical "privileged" access to its meaning. This access provides the needed justification:

pp 46-47 "Language and Reality: Devitt and Sterelny"