First published in 1921, the Tractatus Logico-Philosophicus is a puzzling, mystifying, exhilarating, and eye-opening philosophical work. Written by the Austrian philosopher Ludwig Wittgenstein (1889-1951), the Tractatus was the first and only book published by its author during his lifetime. Other works of his have appeared posthumously, such as the Philosophical Investigations, On Certainty, and The Blue and Brown Books, but the Tractatus was the work which established Wittgenstein's thoughts in the philosophical world at hand. And curiously, the ideas in the book influenced not only philosophers but also scientists, mathematician-logicians, and theologians.
In a broad sense, the Tractatus is concerned with meaning and clarification. To give a simple example, a sentence such as, "The Moon orbits the Earth", makes sense. On the other hand a sentence such as, "Flugblogs grying into the noths", makes little if any sense. The second sentence, while appearing to obey the rules of grammar, doesn't show a sense in the way that the first one does. Why so? What are the conditions that a sentence must meet if it is to have a sense at all? If both examples of mine fit the conditions of being a sentence, maybe we should differentiate between a sentence and a proposition. This differentiating between sentences and propositions was considered by various philosophers to be very important indeed. Sentences just have to be grammatical; they don't necessarily have to make sense (at least, according to some). Propositions, rather, can be thought of as the sense of the sentence; it's what we know when we understand a meaningful sentence. So, it's with propositions and how they "picture the facts" that the Tractatus is concerned, in detail.
One of the main tools that Wittgenstein uses in the book is formal logic. With logic, he aims to reveal some sort of underlying logical form of ordinary sentences. When sentences are confused, like my Flugblogs-sentence, they stray far and wide from this logical form, thus making them nonsense. Another key element that makes a sentence nonsense is when it doesn't "picture" any facts at all. We might say that reality consists of stuff (medium-size dry good!). The moon-sentence above "pictures" something in reality, but the Flugblogs-sentence doesn't. It shows nothing at all. But we have to keep in mind Wittgenstein's distinguishing between a sentence which is nonsense and one which is senseless. The Law of Excluded Middle, "Either P or not P", is senseless, but it's not a meaningless or useless string of words; it plays a role in formal logic. However, "The Ultimate is unending" and "Colorless green ideas sleep furiously" are nonsense: they don't picture any facts at all, and they don't play any sort of role in explaining anything, really. They're just metaphysical rambling of some sort. (It's these nonsensical sentences that some have found problematic, since theology and ethics could be lumped in the category of nonsense. But Wittgenstein comments that the Tractatus can be given an (positive?) ethical reading.)
This idea of a sentence not picturing a fact follows from a previous essay of another man's thoughts: "On Denoting" by the English philosopher-logician Bertrand Russell (1872-1970). In that work, Russell shows that a sentence's ordinary form may in fact be misleading. Through logical analysis, Russell transformed the ordinary sentence "The present King of France is bald" into "∃x[(Kx & ∀y(Ky → y=x)) & Bx]". Wittgenstein had this basic theory of sentence analysis in mind when writing his Tractatus. Indeed, "All philosophy is a 'critique of language'...It was Russell who performed the service of showing the the apparent logical form of a proposition need not be its real one." (T 4.0031)
The Tractatus is not a walk in the park: you need to have some philosophical and logical bearings before you can fully grasp it all. That said, its overall presentation is intriguing. The book consists of seven theses, numbered one through seven. He then comments on these theses, numbering them according to the thesis it's a comment on. The end result looks like a series of well-ordered aphorisms.
Seeing it more of an "artistic rather than a scientific achievement", the German philosopher-logician Gottlob Frege (1848-1925) remarked on the "peculiar form" of the Tractatus. Russell's introduction to the book, differing in content and form in certain respects, was greeted with disdain by Wittgenstein. Perhaps, thought Wittgenstein, something was lost in translation, thus explaining Russell's "misunderstandings" of the book. The structure of the book (theses and comments) wasn't the usual sort of thing one found in philosophy books (well, Friedrich Nietzsche's works are decidedly anti-systematic for subversive purposes). The Tractatus deliberately avoids constructing a grand philosophical system; rather, it aims at clarifying certain things and the relationships they share. Wittgenstein always avoided building grand philosophical systems, for such an activity seemed to distort the objects of study, thus systematically misleading us into false problems and false answers--we become mired in endless confusions. By presenting seven theses and then commenting on them, Wittgenstein's aim was to avoid the usual philosophical pitfalls that may come with system-building. The Tractatus, while systematic, isn't a philosophical system--a grand theory.
However, some years later Wittgenstein came to realize that there was something wrong with the some of the ideas in the Tractatus. It seemed to work with only a very small fragment of language: namely, declarative sentences. It didn't work with ordinary sentences such as "Let's go!" or "I like this show" or "I name thee 'Version Vibrant'!" Some sentences, we notice, don't even purport to name anything; that's not how they work. The Tractatus, in Wittgenstein's view, misrepresented language as a whole. With that in mind, his thoughts gradually culminated in the Philosophical Investigations, where language is no longer understood as having a single, logical essence as represented in the Tractatus. However, there is a continuation between this work and his later works, as mentioned above.
In any event, it was this book that first brought its author to the attention of many others. It's often seen as one of the pillar stones in the philosophical movement called "Logical Positivism", a decidedly scientific philosophy. Carried to extremes, Logical Positivism resulted in the English philosopher Alfred Jules Ayers' (1910-1989) book Language, Truth, and Logic, a book that rejected traditional metaphysics, theology, and morality. It was all nonsense! Wittgenstein, however, didn't exactly banish theology and morality from the map altogether when we completed the Tractatus (hence, the theological interest in the book). Indeed, there were things that were mystical. Was there actually something beyond our abilities to speak of them? On this point, I'm not completely sure, but I don't attribute to the early Wittgenstein the view that almost everything is nonsense. Rather, our talk of certain things tends to have a nature unlike the talk of science. To speak of certain things in a certain formal manner is to lose the character of what you find to be important.
In sum, I find the Tractatus to be a book which I return to again and again. Just when I think I've arrived at a fairly clear idea of what it's doing, it tells me that I should be doing something else. I suspect that in time I'll call some parts of this write-up into question, as well. When viewing the Tractatus and his other books as works of clarifications which lead to further genuine understanding, I would recommend his work to anyone who's open to new perspectives on familiar quandaries.
