The Non-existence of the Internal World

A natural place of retreat once the reality of the mind-independent world has been challenged is that of the certainty of our inner world, a world which, we assume, is perfectly transparent to us and over which we have complete control, which provides a sharp contrast with an external world of which we have limited knowledge, and which frequently resists our attempts to influence it. The second chapter considers a set of reasons against the existence of this kind of internal world. I consider arguments critical of introspective certainty and query the existence of a substantial self that acts as a central unifier of our mental life. The chapter concludes that a foundation in the internal world remains elusive: our introspective capacities do not give us any more of a secure grasp of an internal world than our five senses perceiving the external world.

The Non-existence of the External World

This chapter begins with an investigation of the reasons for the presumed certainty of the existence of the external, mind-independent world around us, and considers a selection of arguments directed against the existence of such an external world. I begin by arguing that we do not need to postulate an external world in order to justify the illusion–reality distinction, or to explain the coherence, intersubjectivity, and efficacy of our perception. The second main part of the chapter focuses on the discussion of different theories of perception (naïve realism, disjunctivism, representationalism) and the ontologies they involve, arguing that ultimately a kind of brain-based representationalism (referred to as irrealism) works best as a theory of perception but that this, somewhat surprisingly, also undermines the justification of a mind-independent world of material objects.

The Non-existence of Ontological Foundations

If both the external and the internal world turn out to be less solid than we initially thought, one thing we can still hold on to is the certainty that something is real, even if the external world is not, and even if we and our internal world are not. This, of course, is the belief in the existence of an ultimate foundation that grounds all existence. This chapter considers a series of challenges to this idea. It begins by evaluating possible arguments for the existence of such a foundation, and then describes attempts to establish its opposite, a non-foundational view of reality, also considering what role this non-foundational view plays in particular sciences, such as mathematics, physics, and cognitive science.

The Non-existence of Foundational Truths

This chapter discusses problems that arise from the assumption that there is a final, ultimately true theory of the world and considers a variety of arguments (connected with the coherence theory of truth, semantic contextualism, and the denial of absolutely general quantification) against it. From this it follows that if there cannot be an ultimately true theory then it also cannot be ultimately true that the world has a non-wellfounded structure. This leaves us with a problem, for it appears as if the theory of the non-existence of the real world we defend in the book as a whole cannot be a final theory either. The chapter closes with a discussion of this final problem, together with some reflections on what the implications of the denial of ultimately true theories are for the ontological or philosophical enterprise more generally.