ABSTRACT This essay presents a concept of rhetoric by accident, which understands accidents in regard to the materiality of affection and in regard to the unconditioned rhetoricity of affectability. The concept of accidental rhetoric put forth depends on the ontological condition of openness, so first affect is stipulated in relation to the porousness of material life to explain the inevitability of affection and provide the basis for understanding rhetoric by accident. Then the accident is defined in alignment with material openness. (...) Rather than consider accidents in terms of human control over contingencies, accidents are defined by the contingency of purposiveness to affection. That affect occurs without purpose means that beings experience rhetoric without a plan. The essay then considers how rhetoric by accident is part of any particular rhetoric's existence, namely as a horizon of evolution and diversification for rhetoric. (shrink)