Informational Scepticism and the Logically Possible

This chapter addresses the question: how do we know that the world really is as our informational constructs tell us it is?—the classic sceptical challenge. The chapter articulates and defends a twofold answer: either informational scepticism is radical (but epistemologically innocuous because redundant); or it is moderate (but epistemologically beneficial because useful). The first part of the chapter reconstructs a historical ‘renaissance of epistemology’ between the two world wars in light of the radical scepticism debate. The second part is entirely theoretical, seeking to solve the problem of radical scepticism. Once the problem has been established, Borel numbers are introduced as a convenient way to refer uniformly to (the data that individuate) different possible worlds. The Hamming distance between Borel numbers is adopted as a metric to calculate the distance between possible worlds. Radical and moderate informational scepticism are analysed using Borel numbers and Hamming distances to show that they are either harmless (extreme form) or fruitful (moderate form). Potential objections are dealt with in a separate section. The conclusion briefly discusses the Peircean nature of the overall approach.