Our title can be read as trivially true, namely, that perceived affordances shape real-time interaction dynamics. A less trivial reading suggests that affordances themselves interact in a shared dyadic field, such that the number and quality of As and Bs affordances are dynamically coupled with bidirectional causality. In dance, martial arts, or team sports agents strategically comodulate each other's affordances while pursuing their aims. In Aikido, where agents try to break their opponents' balance, this trade-off globally approximates a zero-sum game—the better A's affordances are, the lousier B's affordances get. The agents are subject to ceaseless cross-causation in this shared field. They seek to obstruct their opponents' options while strategically enabling, augmenting, and sculpting their own by employing subtle perceptual manipulation skills, redirecting force, brinkmanship, and switching techniques opportunistically. To overcome static views, we conceptualize affordances as cascading and having fluid onsets; we also identify nested affordances in goal hierarchies and describe a spectrum of affordance functions. Ultimately, we suggest rethinking the ontology of affordances as being sensitive to dynamic engagements, hence defined relative to interpersonal emergence.