In this paper, I will present and defend an argument from the conditional character of inferential justification against the version of epistemic infinitism Klein advances. More specifically, after proposing a distinction between propositional and doxastic infinitism, which is based on a standard distinction between propositional and doxastic justification, I will describe in considerable detail the argument from conditionality, which is mainly an argument against propositional infinitism, and clarify some of its main underlying assumptions. There are various responses to be found (...) in Klein’s works to this argument, and my aim is to show that none of those responses can be plausibly held without infinitism losing its title to being a genuine non-skeptical alternative. (shrink)