"But if we had to name anything which is the life of the sign, we should have to say that it was its use."
Here, Wittgenstein takes issue with the usual explanation for how words are infused with meaning. Words on their own are merely sounds or scribbles on paper, but somehow these lifeless objects can become the source of fruitful communication. The typical explanation for how scribbles become meaningful is that the mind processes the scribbles or sounds and gives them life. Wittgenstein suggests that this mentalistic conception of meaning is fundamentally confused, saying that we cannot understand how words connect with reality by alluding to the mind. Rather, Wittgenstein says, words have meaning because they are used within the context of a language. It is not their existence in the mind that gives them life, but their use in a language. A great deal of a word's meaning depends on when we say it, under what circumstances, and within the context of what sentence. Words are first and foremost related to one another, and not to the things they denote.
"Philosophy, as we use the word, is a fight against the fascination which forms of expression exert on us."
Wittgenstein thinks of philosophy as a means of clarifying the different uses of words so that we do not confuse grammatical similarity for semantic similarity. That is, he wants people to avoid the common trap of allowing one form of expression to influence our understanding of another form of expression. We should not hear the sentences, "A has a gold tooth" and "A has a toothache" and assume that both sentences are talking about similar things. That is, we should not give in to the impulse to think of a toothache as something that can be looked for, investigated, and analyzed in the same way as a gold tooth, which is a physical object as a toothache is not, and so cannot be analyzed as a toothache can. Philosophy must help us to appreciate the different uses of different words, and make us wary of assuming that what holds in one case must necessarily hold in others.
"Our method is purely descriptive; the descriptions we give are not hints of explanations."
Wittgenstein says this at the end of the first part of the Brown Book, which consists almost entirely of language games that show the variety of different uses of a word. For instance, there is no one paradigmatic case of "reading": there is instead a whole family of uses that share certain similarities. After giving a number of examples of different uses of the word "read," Wittgenstein warns us that he is not providing these examples so that we can identify what they all share in common. His method is to highlight differences, not to identify fundamental similarities. He wants to show that philosophy should not and cannot identify hidden essences, but only highlight—by means of the descriptive method of language games—that there are no hidden essences, only variegated surface features.
"We need have no reason to follow the rule as we do. The chain of reasons has an end."
Wittgenstein notes here that if we need rules to help us interpret general systems of signs like writing and numbers, then we must also need rules to interpret these rules, and further rules to interpret this second set of rules, and so on. For instance, if in writing down the series of cardinal numbers you need to refer mentally to the rule "Add one" in order to write the next number in the sequence, you must also mentally refer to the rule that tells you how to interpret the rule "Add one." Wittgenstein shows us that providing general rules is not an end-all explanation for how to proceed. Rather, we simply behave the way we do out of convention.
"Understanding a sentence means getting hold of its content; and the content of the sentence is in the sentence."
Wittgenstein says that understanding a sentence is not necessarily a mental act. That is, there is no mental act that constitutes "understanding" a sentence. Wittgenstein asserts that understanding, like meaning and believing, fundamentally has to do with the use and context of a sentence, and not with some mental mechanism. Saying you read a sentence by "understanding" it means that you are falsely linking the act of understanding with something outside the sentence itself.