“Computer systems are, like many other things in engineering, constructed by composition,” computer researchers F.X. Lindner and Sandro Gaycken have written. That line, intended for switched-on digital systems, in fact fits most of our world. Nearly everything around us, from cities to telephone networks to refugee waves, are assembled by composition. Curriences are layered with encryption. Refugee dreams carved from photosharing and refined with GPS. Composition in this way breeds new vulnerabilities, new points of contact and this rather astonishing result, one we're not prepared for in any sense: “In a composite system there is no critical gate,” Lindner and Gaycken explain. “Everything is a gate.”299 239 “Everything is a gate”: Lidner and Gaycken, p. 56 166 HOUSE_OVERSIGHT_018398