Sidman"s (1971) pioneering work on stimulus equivalence and emerging relations ignited the field of behavior analysis. Since his original work, three alternative views regarding the explanation of the emergence of untrained relations have appeared in the behavioral literature: relational frame theory (Hayes, Barnes-Holmes, & Roach, 2001), naming (Horne & Lowe, 1996), and joint control (Lowenkron, 1984). However, despite compiling over 40 years of data on replications, extensions, variations, and applications of these four conceptually distinct views, consensus on the analysis and identification of the relevant sources of control responsible for the emergence of new behavioral relations remains elusive. Dougher, Twohig, & Madden (2014) open their Editorial introducing the special issue of JEAB dedicated to stimulus-stimulus relations with, "One of the great challenges for a behavioral science is to provide an account of emergent stimulus-stimulus relations not explained by primary stimulus generalization" (2014, p. 1). The current paper will suggest that Skinner's (1957) analysis of private events and multiple control, along with other Skinnerian concepts, provides the sought after account of emerging relations. Several procedures for quantifying private events and demonstrating their potential role as additional independent variables (multiple control) in matching-to-sample preparations will be presented.