Impure Infinitism and the Evil Demon Argument

Husein Inusah

doi:10.18267/j.e-logos.428

Abstract

The central thesis of this paper is that the modus ponens reductio argument does not clearly favour impure versions of infinitism. The nub of the modus ponens reductio argument is as follows: an infinite series of justified reasons by itself is vulnerable to the modus ponens reductio in the sense that one can construct an infinite chain of reasons supporting both an affirmative and denial of proposition, say p. The problem here is that, as Aikin urges, pure versions of infinitism do not possess the requisite resource to eliminate one of these chains of infinite reasons. The upshot is that pure versions of infinitism are not able to differentiate between an infinite series that is truth conducive and the ones that are not. Accordingly, Aikin promotes an impure infinitism over pure infinitism because, as he opines, impure infinitism has the requisite resources to eliminate one of the infinite chains of justified reasons and rids itself of the threat of the modus ponens reductio. In the following discussion, I submit that although Aikin seems quite successful in this venture, his version of impure infinitism faces a similar setback, in the form of the new evil demon problem, which is equally fatal to it as that which the modus ponens reductio wrecks on pure versions of infinitism.

Highlights

The principal idea of all pure versions of infinitism2 is the claim that an infinite series of reasons by itself is productive of justification
By granting Aikin’s argument some initial credibility upon the concession that the modus ponens reductio argument yields some unpalatable consequences on pure versions of infinitism, I submit that the triumph of impure infinitism is short-lived because there is an argument of equal weight of devastation as that which the modus ponens reductio argument wrecks on pure version of infinitism
As I have shown, the main concern for Aikin’s preference for foundational basic belief is to insert, so to speak, a truth conducive resource that is able to mark out whether an infinite series is truth conducive or not. This strategy is to ensure that we have a brand of infinitism that is both inferentially relational, in the sense that it endorses the idea that inferential relations between beliefs is productive of justification, and factive, in the sense that it reflects the truth of one’s justified series of infinite reasons. On this assumption I take Aikin’s epistemic argument to possess, in a loose sense, both an internalist and externalist ingredients of justification where the internalist part concerns the inferential relation between beliefs which are in a way construed to be internal to the perspective of the agents and the externalist aspect which appears to embrace an external resource meant to ensure that an infinite series is justified in a way that makes it objectively likely to be true.11The upshot is that this type of infinitist theory of justification is able to retain its mooring with truth since for Aikin “justification, and an analysis of it, should entail a connection between it and truth” (2011, p. 106)

Summary

Introduction

The principal idea of all pure versions of infinitism is the claim that an infinite series of reasons by itself is productive of justification. Aikin contends that we reject the pure infinitist thesis on the assumption that an infinite series by itself is not able to mark out the difference between a series of reasons that is truth conducive and the ones that are not. For this reason, we may require additional resources which, in addition to the infinite series, will yield justification. The point is not to make a case for pure versions infinitism, but rather to argue that the modus ponens reductio does not insulate impure infinitism from the fatal consequences of other objections such as the one that will be raised against it in the following discussion. It will follow from the arguments raised that on the basis of comparative merit in solving the epistemic problem, both pure and impure versions of infinitism suffer similar setback

Pure infinitism and the Modus Ponens Reductio Argument3

Impure Infinitism and the New Evil Demon Argument13

Conclusion