The primary aim of this essay is to present and defend "virtualism" – essentially, the claim that the brain is a virtual reality engine, meaning that the world of experience is, literally, a virtual reality somehow computationally generated by the brain. The most challenging objection to this theory is that it undermines itself by having to admit its own virtuality, i.e., untruth. In preparing my defence against this, I introduce "epistemological fictionalism" as an attempt at establishing a first philosophy based on global skepticism, inspired in particular by the ancient skeptics and George Santayana. The entire first part of the essay's two parts deals with epistemological fictionalism, the problem of justifying belief in general, and my reply to the objection that virtualism is self-undermining. In the second part, virtualism is finally expounded, and a wide range of philosophical consequences are explored. In most of what I discuss here, I rely heavily on Antti Revonsuo and Thomas Metzinger.