Vows play a central role in Buddhist thought and practice. Monastics are obliged to know and conform to hundreds of vows. Although it is widely recognized that vows are important for guiding practitioners on the path to enlightenment, we argue that they have another overlooked but equally crucial role to play. A second function of the vows, we argue, is to facilitate group harmony and cohesion to ensure the perpetuation of the dhamma and the saṅgha. However, the prominence of vows in the Buddhist tradition seems at odds with another central part of the doctrine. For vows, like other promises, seem to involve representing a persisting self as the individual who undertakes the vow. And to explicitly appeal to a persisting self conflicts with one of the most important philosophical commitments of Buddhism – the no self view. We argue though that once we articulate the details of how vows generate behavior that conforms to them, we can see that no appeal to the self is required to internalize and act on vows.