The sociologist Teresa Gowan spent years getting to know a community of homeless recyclers in San Francisco's Dogpatch neighborhood, which she describes in her book "Hobos, Hustlers and Backsliders: Homeless in San Francisco." Now the neighborhood is gentrifying, and many of the homeless have been driven out. Teresa and I revisited Dogpatch to talk about her work there, to see how things have changed and to find out what's happened to the homeless. As we walked, we talked: not just about homelessness but also the ways we speak about it and how they hem us in; the meaning of work; class and underclass in America; and the not-so-heartening history of attitudes toward poverty and "vagrancy." Part 1 of 2.