I compare Locke's views on the nature and powers of the self with E. J. Lowe's view, ‘non-Cartesian substance dualism’. Lowe agrees with Locke that persons have a power to choose or not to choose. Lowe takes this power to be non-causal. I argue that this move does not obviously succeed in evading the notorious interaction problem that arises for all forms of substance dualism, including those of Locke and Descartes. However, I am sympathetic to Lowe's attempt to give a metaphysical account of a robust sort of agency that would explain how human beings might be genuinely autonomous.