LUDWIG WITTGENSTEIN (1889-1951) is a celebrated figure in 20th-century philosophy. A member of a wealthy and cultured Viennese family, he trained as an engineer. But he soon became interested in problems of logic and in 1911 began intensive work with Bertrand Russell at Cambridge. He completed his first book, the remarkable Tractatus Logico-Philosophicus, in 1918 while in active service with the Austrian army in the First World War.

In the years after the war he was successively a gardener, an elementary school teacher and an architect. He suddenly returned to Cambridge in 1929 to resume philosophical research in writing and lectures. Although none of this writing was published until after his death, his new thinking became influential in British and American philosophy in the 1930s and 1940s, principally through the impact of his Cambridge lectures. Collections of notes, taken of those lectures by various students, are now being published.

The notes for 1930-1932, edited by Desmond Lee, exhibitbit at first a striking continuity with the Tractatus: language consists of propositions; a proposition is a picture of reality; a proposition must have the same logical multiplicity as the fact which it describes; thought must have the logical form of reality.

But new concerns soon appear. What is the relation of the logical grammar of language to reality? The application of grammar to reality is not shown by the grammar; a picture does not contain its own application.

"In all language," Wittgenstein says, "there is a bridge between the sign and its application. No one can makee this for us; we have to bridge the gap ourselves. No explanation ever saves the jump, because any further explanation will itself need a jump."

Can grammar be justified? Can we say why we use just these rules of grammar and not other ones? Is the logic of our language to be justified on the ground that it fits the nature of reality? No.

"Our justification could only take the form of saying 'As reality is so and so, the rules must be such and such.' But this presupposes that I could say 'If reality were otherwise, then the rules of grammar would be otherwise.' But in order to describe a reality in which grammar was otherwise I would have to use the very combinations which grammar forbids. The rules of grammar distinguish sense and nonsense and if I use the forbidden combinations I talk nonsense."

The Lee notes contain some memorable remarks. For example, Wittgenstein is reported as saying that in philosophy "all that is not gas is grammar." But, for the most part, the notes are terse, with little elaboration.

Not so with the notes for 1932-1935, edited by Alice Ambrose. Here there are extended discussions of such topics as the nature of logical laws, the attempt by Russell and Gottlob Frege to define the concept of number, and Wittgenstein's view that the propositions of arithmetic and geometry are rules of language. Many examples are worked through. Wittgenstein's discussions display marvelous lucidity, ingenuity combined with simplicity, and an impressive mastery of the material. One feels the excitement of the lectures.

In the Ambrose notes there is a discussion of the notion of understanding a word, and of the relation of this to knowing how to use the word. Wittgenstein argues against the temptation to think that understanding a word is some process or disposition in the brain that enables one to use the word correctly. Many other philosophical puzzles are studied. For example, whether I am identical with my body. Or whether in thinking that something is logically impossible we are conceiving the inconceivable. There are striking comments about the nature of philosophy, one of which is the following:

"The business of philosophy is to rid one of those puzzles which do not arise for common sense. No philosopher lacks common sense in ordinary life. So philosophers should not attempt to present the idealistic or solipsistic positions, for example, as though they were absurd -- by pointing out to a person who puts forward these positions that he does not really wonder whether the beef is real or whether it is an idea in his mind, whether his wife is real or whether only he is real. Of course he does not, and it is not a proper objection. You must not try to avoid a philosophical problem by appealing to common sense; instead, present it as it arises with most power. You must allow yourself to be dragged into the mire, and then get out of it. Philosophy can be said to consist of three activities: to see the commonsense answer, to get yourself so deeply into the problem that the commonsense answer is unbearable, and to get from that situation back to the commonsense answer. But the commnsense answer in itself is no solution; everyone knows it. One must not in philosophy attempt to short-circuit problems."

These two collections of lecture notes are welcome additions to the growing material on Wittgenstein's philosophical work after 1929.

But Gerd Brand's book is something else. Brand's aim is to present the "inner unity" of Wittgenstein's thought by assembling themes from Wittgenstein's "total work," employing copious quotations and paraphrases, plus the guidance of Brand's own interpretations. Brand has, however, no apparent perception of the major changes in Wittgenstein's thinking from the Tractatus, through Philosophical Remarks, Blue and Brown Books, Philosophical Grammar, to Philosophical Investigations, Zettel, and On Certainty.

Even worse, the fine texture and compressed energy of Wittgenstein's sentences are lost in the welter of Brand's turgid 'interpretative' comments. In a chapter called "Temporality" there is this kind of pretentious rubbish:

"Time is, therefore, that in which sameness is given to me, namely, in difference. Sameness is generally only in difference. Only in recognition is identity shown. Recognition is, therefore, what is primary and identity is what is secondary."

This and similar remarks bear no resemblance whatever to the supposedly supporting passages in Wittgenstein cited by Brand. When Brand does succeed in producing a readable sentence, as often as not it is a gross misunderstanding of Wittgenstein. For example, Brand says, "One cannot speak without thinking and one cannot think without speaking. If I think, I am speaking internally." This is an absurd impression of Wittgenstein's acute reflection on the relation of thinking to speaking.

With the accumulation of books on Wittgenstein it was perhaps inevitable that a work like Brand's would be written. But it is dismaying that a reputable publisher should accept it, and also have the effrontery to label it The Essential Wittgenstein.