Despite the broad range of resources they draw on - from geology, Riemannian spaces and metallurgy to psychoanalysis, literature and the game Go - Deleuze and Guattari nonetheless consider themselves to be doing philosophy. In What is Philosophy?, Deleuze and Guattari set out to answer precisely that question. Jeffrey A. Bell explores their answer, that it is the 'art of forming, inventing and fabricating concepts'. In so doing, he draws out the issues at play in their other writings.