Philosophical Investigations, reading it together. §69
Wittgenstein keeps saying the same things, only from different angles. It seems that philosophers and others get hung up on the form of the proposition/statement, as opposed to the function of the proposition/statement, word, or concept. Clarity of thought is not about some very precise definition, which as it turns out is generally impossible. This is clearly observed in our use of the word game, which doesn't have clearly defined borders. On the other hand, clearly defined borders may be drawn if we're talking about a particular kind of game, say chess. However, the tendency for philosophers is to look for unifying principles, or some theory that sums up the concept in some neatly defined idea.
As Wittgenstein points out, someone might say that before we come to understand these unifying principles or theories, we didn't have a very exact definition or an exact measure, but then the problem raises it's ugly head again, what do you mean by exact. So, the problem continues because we aren't seeing the social nature of language in the stream of life.
There are similarities in the Tractatus and the PI in that Wittgenstein is still trying to mark out the limits of sense. In the Tractatus he sets out the limit of language, but in the PI he speaks of the limits (plural) of language, which are found in how we use language. These limits (in the PI) are seen in the various uses of propositions, words, and concepts, they are open to view. They are not hidden, as in the Tractatus, but open to view in the stream of life.
Another similarity between the Tractatus and the PI, is that Wittgenstein is still trying to understand the function of language. In the PI there is no absolute method of determining sense from nonsense, no formal boundary as he set up in the Tractatus. Something only makes sense (in the PI), or is nonsense in a particular language-game. Even the term make sense is vague, just as the term game is vague. Just as the word game would alter its meaning from context to context, so making sense would alter its meaning from context to context, or from language-game to language-game.
This is an expanded version of PI 69, pulling together a general overview.