Foundationalism in moral epistemology is a core tenet of ethical intuitionism. According to foundationalism, some moral beliefs can be known without inferential justification; instead, all that is required is a proper understanding of the beliefs in question. In an influential criticism against this view, Walter Sinnott-Armstrong has argued that certain psychological facts undermine the reliability of moral intuitions. He claims that foundationalists would have to show that non-inferentially justified beliefs are not subject to those defeaters, but this would already constitute (...) a form of inference and hence undermine the possibility of noninferential justification. The goal of my paper is to defend foundationalism against Sinnott-Armstrong’s criticism. After presenting his challenge, I first argue that the most promising objection to it fails. This objection makes the case that defeater-defeaters are not part of the justification, but merely preserve the justification which the original claim provides. I object to this argument by distinguishing between weak and robust defeaters; only weak defeaters, I argue, fall outside the scope of justification, and it is an open question whether Sinnott-Armstrong’s defeaters fall into that category. This leads the way to my own criticism of Sinnott-Armstrong’s challenge: foundationalists in moral epistemology are entitled to the use of defeater-defeaters as part of the justification for moral beliefs as long as those defeater-defeaters themselves do not entail moral claims. Therefore, Sinnott-Armstrong’s challenge does not undermine foundationalism. (shrink)