Jonathan Dixon

The Cartesian arguments for external world skepticism are usually considered to be significant for at least two reasons: they seem to present genuine paradoxes and that providing an adequate response to these arguments would reveal something epistemically important about knowledge, justification, and/or our epistemic position to the world. Using only premises and reasoning the skeptic accepts, I will show that the most common Cartesian argument for external world skepticism leads to a previously unrecognized self-undermining dilemma: it either leads to a reductio ad absurdum, or to avoid this reductio the skeptic must accept that this argument is epistemically idle—it does not provide any support for external world skepticism. Either way, this Cartesian argument cannot legitimately threaten or even call into question our beliefs about the external world. And thus, either way, this Cartesian argument for external world skepticism is not epistemically significant—it is not a genuine paradox and adequately responding to it need not reveal anything epistemically important.

While many have argued that moral disagreement poses a challenge to moral knowledge, the precise nature of this challenge is controversial. Indeed, in the moral epistemology literature, there are many different versions of ‘the’ argument from moral disagreement to moral scepticism. This paper contributes to this vast literature on moral disagreement by arguing for two theses: 1. All (or nearly all) moral disagreement arguments share an underlying structure; and, 2. All moral disagreement arguments that satisfy this underlying structure cannot establish moral scepticism because this underlying structure leads to a previously unrecognized reductio ad absurdum. In short, I argue that this reductio argument (very likely) refutes all versions of the moral disagreement to moral scepticism argument in one fell swoop.

Conciliationism is the family of views that rationality requires agents to reduce confidence or suspend belief in p when acknowledged epistemic peers (i.e. agents who are (approximately) equally well-informed and intellectually capable) disagree about p. While Conciliationism is prima facie plausible, some have argued that Conciliationism is not an adequate theory of peer disagreement because it is self-undermining. Responses to this challenge can be put into two mutually exclusive and exhaustive groups: the Solution Responses which deny Conciliationism is self-undermining and attempt to provide arguments which demonstrate this; and the Skeptical Responses which accept that Conciliationism is self-undermining but attempt to mitigate this result by arguing this is either impermanent and/or not very worrisome. I argue that, by Conciliationism’s own lights, both kinds of responses (almost certainly) fail to save Conciliationism from being self-undermining. Thus, Conciliationism is (almost certainly) permanently self-undermining. This result is significant because it demonstrates that Conciliationism is likely hopeless: there is likely nothing that can save Conciliationism from this challenge. I further argue that Conciliationism, like any view, should be abandoned if it is (almost certainly) hopeless.

This dissertation concerns whether philosophy as a discipline can, and does, produce philosophical knowledge. Specifically, this dissertation concerns several prominent arguments for philosophical skepticism. Some support philosophical skepticism by arguing that the philosophical practice of appealing to intuitions to justify philosophical beliefs is illegitimate because either intuitions are not a legitimate kind of evidence or intuitions are an unreliable source of justification. Others argue that philosophical knowledge is untenable because philosophers rarely, if ever, resolve their philosophical disagreements despite spending their professional lives attempting to do so. In brief, the purpose of this dissertation is to defend philosophical knowledge from these arguments by showing that philosophical knowledge is not threatened by either intuition or disagreement skepticism.