The last half of twentieth century Anglo-American (i.e. British and American) thought is often characterized as what is often called the linguistic turn. This describes a common trend of turning to language as the main subject of study in a diverse range of areas including literature, anthropology, sociology, and gave rise to fields such as linguistics and semiotics. As an example of this dominance of this linguistic turn, consider how even fields like biology and zoology grew to include studies of questions such as whether animals have language? Issues about language arose in many aspects of life including politics (free speech vs. hate speech) and social morality (sexism in language vs. political correctness). Which ever way one's opinion goes, such issues are framed in terms of the language. The effects of the linguistic turn are everywhere.
In philosophy the linguistic
turn indicates intense interest in questions such as:
limits of my language mean the limits of my world.
A key statement in this preface is that he is seeking to draw a limit to thought. That does not mean to create restrictions for thinking. Instead Wittgenstein is setting out to show that that by mapping the possibilities and impossibilities of thought, we can describe the limits of reality. After all, if we cannot think it then it cannot be -- in our world at least. That is, for something to exist in the world (in actuality or imagination), it must be potentially thinkable by us, otherwise it could never register on our minds at all.
Now, someone might reply; "Well but what if there are things in existence that are beyond our human ability to imagine or conceive?" That seems like a fair objection, though now we must ask the obvious question; "What do you have in mind? Can you give an example?" The answer to that must be "No." If it is not thinkable, then no one can describe it or exemplify it in anyway. So, while the objection seems as if it refers to something, it really has no referent at all. This is what Wittgenstein calls nonsense. No because it is silly, but because a sentence has a sense just in so far as it refers to some possible state of affairs in the world. Even if it is false or ridiculous, a sentence has sense if it refers to a possible combination of elements. This is part of Wittgenstein's explanation of what meaning is.
As already noted, the words;
seem like an ordinary sentence, so we are likely to take it seriously (i.e. grant that it could be true). Yet, Wittgenstein's analysis shows that such a string of words has no referent (does not refer to anything) and so is without a sense -- is senseless -- is nonsense -- is meaningless. Such a sentence is neither true not false. Because only sentences with a sense can be true or false (the sense is what truth and falsity is based on).
This sort of thinking can make many people's heads swim -- you sort of get it but cannot quite pin it down. That is an effect that comes from running up against the limits of language -- these are not limits that we create, they are the limits of what language can do. Wittgenstein depicts a model of the human mind such that "the limits of my language mean the limits of my world." Thus, through the philosophical study of language, we can identify the boundaries of philosophical thought.