Exactly what sort of Justification is required for knowledge is controversial. For Descartes, the justification needed for a to count as knowledge is indubitabilityIn other words for a belief to be knowledge the truth of the belief must be beyond any doubt whatsoever, it must be 100% certain Descartes' view too extreme? so, why think we have to be that sure? Can we know things about which we aren't certain? so, what sort of justification is required for knowledge?