I suspect that whatever cannot be said clearly is probably not being thought clearly either

--- Peter Singer in "Ethics in the Real World: 82 Brief Essays on Things That Matter" (2016), quoted in The Economist review 17 September 2016

In the context of the review:

Mr Singer’s latest book, “Ethics in the Real World”, is a collection of 82 essays, each rarely more than three or four pages long. As such, it is an accessible introduction to the work of a philosopher who would not regard being described as “accessible” as an insult. As Mr Singer notes drily in the introduction, “I suspect that whatever cannot be said clearly is probably not being thought clearly either.”