The latest book by linguist Steven Pinker, When everyone knows that everyone knows...Published in Spanish by Paidós, this book deals with common knowledge, the cognitive system that allows us to be aware of what others know. That is, what we know everyone knows. These are the kinds of mental faculties that allow us to navigate life as couples, families, in society, and as citizens. Without an awareness of what we think and what we know others think, it is impossible to share a common space, impossible to live with others. It is necessary to establish tacit consensus, norms we follow even before they are codified in law. This is why common knowledge becomes an essential vector of freedom of expression, academic freedom, and freedom of thought.