Three-part seminar and discussion with freethought (Stefano Harney, Adrian Heathfield, Massimiliano Mollona, Louis Moreno, Irit Rogoff, and Nora Sternfeld) and guest Denise Ferreira da Silva. Over three consecutive sessions, freethought introduces the concept and applications of “spectral infrastructure,” a term that alludes to the hidden and invisible textures that sustain an undefinable and disruptive quality in an otherwise seemingly efficient organism. Continuing from the collective’s long-term research into material and organizational infrastructures, spectral infrastructure pursues an understanding of the “ephemeral glue,” or that which is invisible, inaudible, and illegible but nevertheless elicits a response and informs a reality that can be found echoing around existing structures. Spectral infrastructure holds things together by underwriting the subjectivity of an institution, of an intellectual and political drive, a beat or a rhythm, a gaze or a gesture, or momentary mutuality or a collective affect. The research moves speculatively from the binding forms of material and data infrastructures toward intangible intensities as a coalescing force.