»When we speak of anything as “free,” our meaning is not definite unless we can say what it is free from. Whatever or whoever is “free” is not subject to some external compulsion, and to be precise we ought to say what this kind of compulsion is. … Legal penalties are, however, in the modern world, the least of the obstacles to freedom of thoughts. The two great obstacles are economic penalties and distortion of evidence. It is clear that thought is not free if the profession of certain opinions makes it impossible to earn a living. It is clear also that thought is not free if all the arguments on one side of a controversy are perpetually presented as attractively as possible, while the arguments on the other side can only be discovered by diligent search.«