It's interesting. Unlike many art historians, I am not a heavy user of philosophy or theory directly in my work. In other words, I don't use theory as a basic overlay or structure for my work, though I am quite fond of using philosophy as a primary source that helps me gain insight into the thinking of the people that I study. As someone whose dissertation is on the nineteenth century United States that has most often been Emerson and the other Transcendentalists, but also frequently includes Marx as well as his German forebears, like Hegel.

In graduate school I got heavy doses of the Frankfurt School, the group of Lacanian-influenced Marxists centered around Althusser (well, also I suppose Lacan himself), and Foucault, and I think all of those groups have had a more general effect on my thinking and worldview. In particular, I often find myself thinking about the operations of ideology in Althusserian terms, though I can't think of a time outside of a seminar paper where I have explicitly cited him in writing.

One contemporary theorist whose work I have cited and will continue to cite is W.J.T. Mitchell, whose formation of landscape as an ideological construction I find quite useful.