What one cannot speak of, one must pass over in silence.
There are a couple of different ways to view this aphorism which shows up in the preface to Wittgenstein's Tractatus. The first is that it is a truism. If one cannot speak of something, then silence is the apparent consequence.
However, I am intrigued by the construction of this sentence. Although I cannot read the German, all translations have the same "pass over in silence."
To be silent is a non-action. To speak is an action. Silence is the cessation of speaking.
However, to "pass over in silence" gives silence an agency as though silence is a movement that one chooses.
Then there is the first half of the sentence: What one cannot speak of. How does one decide on the subjects that one cannot speak of and what is the criterion of speaking?
Given that the sentence is within the preface to the Tractatus, there is the standard of pure logic which Wittgenstein is laying out. This would limit very much what one could speak of. However, in Culture and Value (and I assume elsewhere) are attempts by Wittgenstein to conceptualize and explore various problems without coming at a clear logic immediately. Culture and Value is riff with numerous attempts at the same problems, a stuttering of the subject. Wittgenstein wrote many times of how he felt he repeated the same topics over and over.
Simultaneously, Wittengstein writes of the limits of language, of the lack of communication. In many ways, the preface to the Tractatus might be said to be mostly concerned with the inability to communicate, whether the problem lies with the subject, the speaker, or the reader (or a combination of the three).