Historic figures were not diagnosed with autism because the term and the scale had not been invented yet. That does not mean that they did not have what we would think of as autism, it is just more difficult to say whether it is true. Let’s look at the facts. Van Gogh was a brilliant artist, not appreciated in his time, who was eccentric, very depressed, manic and cut his ear off in a fit of angst. This does not lead one to believe he was autistic. Probably more along the lines of bipolar leaning toward the major depressive side of things.