<p>Mind uploading involves two technological approaches: brain simulation and brain replacement. To achieve immortality, these approaches must metaphysically satisfy the requirements of phenomenal consciousness and personal identity. This paper finds that to meet these requirements, brain simulation presupposes the truth of role functionalism for mental states and ultra-role-functionalism for identity, while brain replacement presupposes the truth of realizer functionalism for both mental states and identity. To adjudicate these functionalist theories based not only on a priori considerations but also on empirical evidence, this paper introduces a confirmation process that moves from empirical observation (i.e., sensory substitution) to science (i.e., sensorimotor enactivism) and then to metaphysics. It finds that realizer functionalism aligns better with empirical observation than role functionalism. If realizer functionalism is a more reasonable theory, it would imply that brain simulation is impossible, while brain replacement remains a possibility. However, realizer functionalism is an empirically constrained metaphysics. While it commits to the metaphysical possibility of brain replacement, our analysis, based on relevant neuroscientific research, argues that it is unlikely to possess such a nomological possibility. Therefore, whether through brain simulation or brain replacement, it is unlikely that humans could achieve immortality through mind uploading.</p>