This document discusses various bioethical boundaries such as human/animal, interspecies, and human/machine boundaries. It explores how boundaries are identified and located, as well as different motives for crossing, blurring, or defending boundaries. Some motives for crossing boundaries include mistake, curiosity, personal advantage, self-fulfillment, and social necessity. Motives for defending boundaries include political strategy, fear of change, and protecting important moral values. The document also examines common reactions when boundaries are crossed such as moral outrage, disgust, anger, excitement, and fear.