Bolter and Grusin's article, though rather short and concise (and somewhat difficult to access, the website kept kicking me off the text for some reason, but I digress), touches on a very deep and multifaceted issue. The first class that encouraged me to reflect deeply on the ideas of virtual and augmented realities was my Philosophy of Mind class in 2009. The class was a combination of metaphysical and epistemological theories which sought to explain the concepts of mind and knowledge and their relationship to reality. Bolter and Grusin's section on virtual reality (those which alienate us from the physical world) contains very distinct parallels to Descartes' rejection of Empiricism. To paraphrase his position from his work Meditations on First Philosophy, Descartes states that he cannot take the integrity or actuality of his sensory experience as granted because he has no guarantee that a demon isn't manipulating his senses, or that he could be dreaming. Many who don't read very much Philosophy see this as a very peculiar and unconvincing argument because they see the likelihood of such an occurrence to be extremely low. However, virtual (and augmented) technologies essentially produce the same dilemma by embedding "pseudo-realities" that are immediate and perceived through our sense faculties within our "actual" or "pure" reality, which is unmediated (or perhaps only to a lesser extent) by reality-shaping technologies. Virtual reality contains the most obvious parallels to Descartes' thought experiment, as it is wholly immersive and alienates one's senses from an unmediated reality.
Augmented reality also contains obvious parallels to Descartes' thought experiment in the sense that it alters sense experience, but I think that augmented reality raises serious questions about the nature of knowledge more so than an empirically grounded reality. The radical application of technology in the form of augmented reality systems may cause us to adopt a more Functionalist-oriented worldview. But within Philosophy, Functionalism is almost universally regarded as an inherently flawed Epistemological theory, to the extent that almost nobody has proposed a serious defense of it in several decades while several crippling criticisms have been levied against it. Of these criticisms, I take John Searle's "The Chinese Room" thought experiment to be the most foundational one (There exists a wikipedia article solely for this thought experiment, I will not attempt to paraphrase it here as it would consume too much space). One potential outcome of augmented reality is that it makes us like the individual in the featureless room, a machine that simply executes commands and acts according to a formal language. Augmented reality could easily take away all of our knowledge and only give us the appearance of knowledge. There is a very fundamental difference between knowing something intuitively and depending upon something to give us relevant information. If one was using an augmented reality system and upon looking at a sign in a completely foreign language (let's say Chinese) and the AR system automatically translated the sign, would it be right to say that the individual reads, speaks, or knows Chinese? I would have to say not at all, for the very same reasons John Searle outlies in his thought experiment. Though this is only tangential to Bolter and Grusin's article, I still think that this is very important to keep in mind when contemplating the nature of technology and immersive mediums in general.