This is a question that has bothered me a lot. Was Daniel Cassidy (author of How the Irish Invented Slang) insane, was he consciously and deliberately dishonest, or was he too stupid to know the difference between real research and idiotic speculation?
It is a tricky one. While there is quite a lot of evidence that Cassidy was a couple of sandwiches short of a picnic, I don’t think we can say that he was completely insane. He managed to write the book and talk at public meetings with a semblance of rationality. His view of the world might have been very strange, but he wasn’t a carpet-chewing crazy.
There is also clear evidence that he was dishonest. He added entire phrases to definitions to make them accord more closely with what he wanted. He adopted unconvincing sock-puppet identities to attack his critics. However, I also get the impression that he actually believed that his ‘research’ was largely right.
Cassidy was certainly stupid. He lacked any knowledge of the Irish language or of linguistics and his conclusions show an astounding inability to think, or to distinguish between bullshit and reality.
So, which is it: mad, bad or stupid? In a sense, I think Cassidy was all three. I never met him, so I am judging purely on the basis of his public persona, but he reminds me of a lot of news stories about people with narcissistic personality disorders, fantasist con-men with an appetite for publicity, an inflated sense of their own importance, the capacity to believe in their own spiel as if it were the truth, an ability to charm and manipulate, and a tendency to turn very nasty when criticised or crossed.