In Radical Skepticism and Epistemic Intuition (hereafter RS&EI), I defend a commonsense response to radical skepticism about our ordinary perceptual and memory beliefs—a response inspired by the 18th-century philosopher, Thomas Reid.Footnote ¹ A distinctive feature of my response is my conscious and explicit reliance on epistemic intuitions. These are like moral intuitions insofar as both are seemings about a certain kind of normative quality—either about the presence of that quality, in a particular case, or about what is required for that quality to be present.Footnote ² (Seemings are conscious mental states consisting of things seeming to you to be—or striking you as being—a certain way; they have the feel of a mental state whose content presents how things really are.Footnote ³) Although I’m an externalist in epistemology, I employ a phenomenal conception of evidence (where evidence consists of our conscious mental states) and I think of epistemic intuitions, and seemings more generally, as part of our evidence. Moreover, the response to radical skepticism offered in RS&EI is intended to be usable by both internalists and externalists in epistemology.Footnote ⁴ Although my explicit reliance on epistemic intuitions is distinctive, I make the case that all of us (including philosophers as well as non-academics) regularly rely on epistemic intuitions, both when we feel the force of radical skeptical objections and when we resist them in commonsense ways.Footnote ⁵

RS&EI has three parts, with parts I and II focusing on inferential antiskepticism and noninferential antiskepticism, respectively. What these two kinds of antiskepticism have in common is a rejection of both radical skepticism and concessive responses to radical skepticism. (Concessive responses to radical skepticism concede that we do not know that we are not radically deceived; but they also insist that, contrary to radical skepticism, we do retain much of the ordinary knowledge we assume we have.Footnote ⁶) Inferential antiskepticism is a nonconcessive response to radical skepticism saying that—although the justification of our ordinary perceptual and memory beliefs requires that they are defensible inferentially via good arguments—these ordinary beliefs are, in fact, justified because they satisfy that requirement. Noninferential antiskepticism is a nonconcessive response to radical skepticism saying that our ordinary perceptual and memory beliefs are justifiedly held noninferentially, even if they are not defensible via any available good arguments.

In part I of RS&EI (“Underdetermination and Inferential Antiskepticism”), which comprises Chapters 2–5, I argue that (i) the best arguments for radical skepticism are underdetermination arguments (which say that our evidence for our ordinary beliefs underdetermines the truth of those beliefs) and that (ii) the inferential antiskeptical response to such underdetermination arguments fails. That response says that the gap between our underdetermining evidence and the truth of our beliefs based on that evidence can be bridged by good arguments. That response fails because (contrary to inferential anti-skepticism) no such arguments are available to us.

In part II of RS&EI (“Particularist Noninferential Antiskepticism”), which comprises Chapters 6–10, I respond to underdetermination arguments for radical skepticism by presenting and defending an intuitionist particularist version of noninferential antiskepticism.Footnote ⁷ To understand the “intuitionist particularist” label, consider the following. Arguments for radical skepticism (including underdetermination arguments) have, as premises, general epistemic principles about what is required for justification; beliefs in these principles are supported by and based on epistemic intuitions. But we also have commonsense epistemic intuitions supporting the falsity of the conclusions of such arguments. For example, we have epistemic intuitions that (contrary to the conclusions of arguments for radical skepticism) our ordinary perceptual and memory beliefs are justified. Which of these epistemic intuitions carry more evidential weight? Methodists and particularists give different answers to this question. Roughly speaking, methodists are those who treat our epistemic intuitions supporting general epistemic principles (e.g., the principles that are used as premises in arguments for radical skepticism) as having more evidential weight than our epistemic intuitions saying that our ordinary perceptual and memory beliefs are justified; and particularists are those who treat our epistemic intuitions about the justification of particular perceptual and memory beliefs as having more evidential weight than our epistemic intuitions supporting general epistemic principles (including those appearing among the skeptic’s premises).Footnote ⁸ The noninferential antiskepticism I present and defend in RS&EI is an intuitionist particularist response to radical skepticism because (a) it relies on epistemic intuitions and (b) the epistemic intuitions it treats as having more evidential weight are those favored by particularists.

In part III of RS&EI (“Skepticism about Epistemic Intuition”), which comprises Chapters 11–13, I consider three skeptical worries about reliance on epistemic intuition.Footnote ⁹ The first skeptical worry takes the underdetermination concerns that (in part I of the book) were applied to perception and memory—and emphasized the gap between our evidence and the truth of the beliefs based on that evidence—and applies them to epistemic intuition, where there is a similar gap. The second skeptical worry highlights disagreements due to differences in epistemic intuitions among people who seem to be approximately on a par in terms of being intelligent, generally well-informed, and competent in responding to evidence. Each of these first two skeptical worries is used to cast doubt on the trustworthiness of epistemic intuition. The third skeptical worry employs the methods of experimental philosophy to cast further doubt on the reliability of epistemic intuition by (allegedly) showing that epistemic intuitions are subject to irrelevant influences of various kinds. I argue that all three of these concerns fail to undermine the rationality of relying on epistemic intuition in the way I do in part II of RS&EI in my preferred response to radical skepticism.Footnote ¹⁰