In this chapter, I advance a non-reductive, proposition-directed, sui generis account of agnosticism called the questioning-attitude account. The questioning-attitude account is non-reductive because it denies that agnosticism is reducible to other mental states like belief, desire, or intention. It is a proposition-directed account because it holds that the object of agnosticism is a proposition, as opposed to a question or another mental state. It is a sui generis account because it holds that unlike belief, which involves an affirming stance towards a proposition, or disbelief, which involves a denying stance towards a proposition, agnosticism involves a distinct questioning stance towards a proposition.