WITTGENSTEIN by Peter Hacker is a 59 page essay on Wittgenstein's view of a particular class of mental processes that comprises pain, intention, belief, understanding, and expectations. The book sets out to establish that this class is an illusion and does not really exist, and if this class does exist, it is not relevant to our usual, ordinary use of the English language.At only 59 pages, the book cannot cover all of W.'s philosophy, for example, there is no commentary on families of resemblances, how words get their meaning, or rule-following. To benefit from Peter Hacker's book, this reviewer recommends first reading the Blue and Brown Books, On Certainty, and the Philosophical Investigations.THE EARLIER VIEW. Pages 3-15 and 40 disclose what W.'s philosophy is reacting against, namely, the views of Descartes, Hume, and others. Earlier views have held that "to exist" is similar to other verbs, such as "to drink." Earlier views held that the property of existence is similar to other properties, such as "to be red." Earlier views held that "the mind" is the name of a thing, and thus had some similarity to other names for things, such as "the brain" or "the penny." (pages 7-11 of Hacker).We learn that Descartes divided human existence into the MIND and BODY. Over the course of a hundred years or so, this was rejected and replaced with the concept that human existence is divided into the brain and body, where the mind resides in the brain, and where the mind contains "inner processes" such as pain, beliefs, desires, where these inner processes reside on a sort of theater stage known as the mind (page 23, Hacker). Or where speaking about what we believe, intend, expect, feel in terms of pain, rests on observing some state or event in one's mind (page 25, Hacker).We learn that the earlier view was that our own pain, beliefs, intentions, desires, are all AUTOBIOGPHICAL statements (page 23, Hacker), and that they are descriptions of our state of mind, just as one might describe one's room (page 34, Hacker).REASONS TO DOUBT THE EARLIER VIEW. W. argues that the notion of an inner theater stage is a fallacy, for the following reasons. If I am in pain, it is impossible to doubt that I am in pain. Nothing counts as doubting whether one is in pain (page 30, Hacker). It is never the case that we say, "I thought I was in pain (or I thought I believed so and so, or I thought I intended such and such), but I was mistaken." (pages 30, 31). W. tells us that statements about pain, beliefs, intentions, expectations, being pleased, promising, are NOT like descriptions of one's self (NOT autobiographical statements, NOT like a description of one's own room) because of the fact that they can never be incorrect (page 34), and secondly, because of the fact that NO skills are needed to apprehend one's pains, fears, intentions, expectations, or the fact that one might believe something (page 35), and thirdly, because they have no particular duration (in contrast, moods and emotional states have particular durations) (page 36). Please note that durations and temporal issues are also discussed in the Philosophical Investigations (pages 163, 149, 169, 175, 179, 184, 185).ON CERTAINTY. Wittgenstein's book, ON CERTAINTY, discloses arguments in additional to those in Peter Hacker's book. "To say, I know that I am in pain means nothing because in the practice of using "to know" you must have some sort of evidence (paragraphs 501 to 504, 555, 564, of ON CERTAINTY). Please also note that Robert Fogelin (page 157, 158 of Fogelin's book on Wittgenstein) tells us that in making a promise, we are NOT reporting that a promise exists in our mind. Here, Robert Fogelin is agreeing with W. that "mental processes" are not relevant to things like promising, expecting, having a pain.PHILOSOPHICAL INVESTIGATIONS (PI). Wittgenstein, in the PI, provides further arguments against inner processes as being relevant to pain, intention, believing, "No process could have the consequence of meaning" (page 186 of PI). Even if there existed something in the mind corresponding to a pain, intention, or belief, this "thing . . . has no place in the language game at all . . . it drops out of consideration as irrelevant." (paragraph 293 of PI). W. discounts that idea that things like pain, intention, beliefs, or expectations, are mental processes. W. writes, "To say of an expectant person that he perceives his expectation . . . would be an idiotic distortion." (paragraph 453 of PI). Also, W. argues, "I see someone pointing to a gun and I expect a bang. The shot is fired . . . so did that bang somehow exist in your expectation? . . . the bang was not so loud as I expected . . . then was there a louder bang in your expectation? (paragraphs 442, 449, 452 of PI).CRITICISM. I think it might be useful if Peter Hacker had made a nice, orderly table showing all the arguments, examples, or thought-experiments, that W. uses to dissuade us that "inner processes" in the mind are relevant to pain, intention, expectation, promising, and the like. Also, Peter Hacker's book does not tell us how Wittgenstein's ideas have been modified by other philosophers, for example, in the years 1960 to the present.