Because we hold individuals criminally liable for infliction of “bodily” injury, but impose no criminal sanctions for infliction of purely “mental” injury, the criminal law rests in large part on a distinction between mind and body. Yet the criminal law is virtually silent on what, exactly, constitutes “bodily injury.” This Article explores the content of the bodily injury construct through the lens of cognitive neuroscience, which poses new challenges to traditional mind-body distinctions. Combining a review of bodily injury definitions in criminal assault statutes and a series of empirical analyses, the analysis finds that: (1) jury-eligible lay people exhibit much confusion and disagreement about what constitutes a “bodily” injury; (2) jury instructions, with different definitions of the term, significantly affect how lay people determine bodily injury; and (3) neuroscientific evidence, if unchecked by a limiting jury instruction, will likely expand the bodily injury concept to include injuries that have traditionally been seen as non-physical. Taken together, the findings in this Article suggest that—if the criminal law were to recognize the biological and thus physical basis for mental injury—the limits of criminal liability for harms against the person might be increasingly contested as the distinctions between mind and body for purposes of criminal liability shift. To avoid this confusion, and the potential injustices that might emerge, the Article argues that legislatures should carefully revisit bodily injury definitions. The Article provides a series of options that legislatures can employ.