While neuroscience continues to make it clearer that mental processes, effects, disorders, and states can be described through physical observation, the metaphysical notion of mind-body dualism still pervades the U.S. legal system. In this Article, I discuss many areas where mind-body dualism holds fast, and others where mind-body dualism has already been explicitly or impliedly rejected. I argue that in most areas, the dualist distinction would have little to no impact on the values the law already describes. However, I argue that rejecting dualism would have an impact on fundamental rights analyses. First Amendment free speech rights, fundamental rights, and substantive due process doctrine, and particularly as related to the negative rights of children and their parents’ rights to raise them, change when seen as involving indelible physical processes. Discussing some relevant Constitutional doctrines, I explain what changes to the analysis follow as a matter of logic, while also discussing normative considerations that would arise. Assuming that dualism is false, I conclude that certain types of now-protected speech and expression would need to be reconsidered because of their potential to physically harm listeners and cause harm generally throughout society. I argue that children should be provided with a robust set of certain negative freedoms due to the physical and sometimes permanent changes that occur in young brains subject to, for example, racist or anti-LGBTQ ideology. When seen as more than merely mental, some of the speech currently protected in the U.S. presents a public health issue that needs to be addressed at the most fundamental level.