so if you look at normal rockwell's paintings, for instance, the people... the men have bumps in the back of their heads. they're not flat headed, because that's part of what used... used to be important for anglo-saxons, the shape of their heads. to be irish and catholic is not a big deal anymore. it was a very big deal in say, 1855, 1860, 1890. so the categories, the importance of the categories, changes over time, and i'm sure it will keep changing. >> hinojosa: and you... you kind of dove right into this. i mean, you've... >> well, it was a slow... >> hinojosa: well, you've been a historian... >> i've been a historian for a long time, yeah. >> hinojosa: ...an amazing historian based at princeton, and yes, you have studied history, but... >> and i've done lots of different books. >> hinojosa: oh, amazing books. >> this is not my first book, yeah. >> hinojosa: sojourner truth, the making of the black american? >> creating black americans. >> hinojosa: creating black americans. >> yeah, southern history across the color line, the united states 1977-1919... >> hinojosa: you've been p