This article is an ethnographic account of the speculative thought of Jane Roberts, a spirit medium or “channel,” important in New Age religion for the books that she dictated at the behest of a personality named “Seth.” At first, she tried to understand her strange subjectivity in psychiatric terms, then went on to elaborate metaphysical concepts to account for it. The author argues that understanding Roberts's concepts in social historical terms risks obscuring their meaning and that comparing them with the related concepts of a credentialed philosopher, in this case Gilles Deleuze, is a more effective way of approaching them. The latter sort of interpretation entails another risk, however, which is that concepts like those of Roberts may get taken for mere illustrations of the arguments made by academic philosophers, whereas marginal thinking of Roberts's kind can form sophisticated bodies of thought on their own. Roberts developed concepts of consciousness and the person that exceed, in ways that this article specifies, anything that Deleuze's work can say about them and thus cast his own arguments in an unanticipated light. This essay's main point is that uncredentialed, marginal thinkers like Roberts should be considered proper objects of both anthropological and philosophical study and should be taken seriously for what they can teach us.