[coolgeek]

> I have a very different view: programming language design is applied psychology, not mathematics.

It's both, and probably more.

As you note, programming languages are the ultimate human-computer interface. They have to serve two masters - the computer's unforgiving hardware, and the inevitably fallible humans attempting to harness the computer's power. Each master requires different types of proof/evidence of the language's suitability to the task.