We need to understand personal identity to develop radical life extension technologies: mind uploading, cryonics, digital immortality, and quantum (big world) immortality. A tentative solution is needed now, due to the opportunity cost of delaying indirect digital immortality and cryonics. However, solving the problem of personal identity is not easy. Human personal identity is a complex thing, not similar to other types of identity, such as that of Theseus ship. First of all, human identity consists of two intertwined types of (...) identity: informational identity, which predicts sameness, and identity of consciousness, which predicts what I will experience in the next moment of time. The identity of consciousness is called "hard problem of identity", and it is because it supervenes on the nature of consciousness. The second feature of human personal identity is that it is observed and measured internally, by identity subject himself. The third is that it evolves in time. -/- The main dichotomy in the views on personal identity and copies can be presented as: either my copy=original or a soul exists. In other words, some non-informational identity carrier (NIIC) may exist that distinguishes the original from its exact copy. Typically, it is often claimed that NIIC is either continuity of consciousness, or soul, or perspective, or the sameness of atoms, or position in space. We create an exhaustive map of identity theories. -/- We demonstrate here that the idea of continuity of consciousness is very similar to the idea of soul, but also has several problems: - Is it the continuity of qualia, of causal processes, of computations or of underlying substrate? - We also show that continuity doesn't prevent the emergence of two future copies if they split smoothly, so continuity does not preserve identity as uniqueness. - Also, continuity doesn't ensure uniqueness as I can continually become someone else. - Continuity + MWI means that I will eventually become anyone, that is, open individualism. - Continuity also can be paradoxically preserved without preserving body and mind as a separate process like flame. - Humans also seems to survive discontinuity during sleep without problems. Nevertheless, continuity appears to be inherent to qualia, emerging after observation but before action, and in planning. Only if continuity of consciousness is an ontological necessity, it can be a valid NIIC, but this is true only in a specific version of solipsism (qualia dust theory). In that case, a specific set of personal qualia becomes the personality carrier. -/- If copy=original then even imperfect copies suffice for personal immortality, as self-recognition becomes the main criterion of identity. -/- Open and closed individualism deny the existence of identity but must reinvent it as "practical identity" and therefore revert to copy=original. -/- To resolve the main dichotomy, we must recognize that personal identity requires an overarching system: God, qualia world, social agreement, or evolutionary fitness. This means that we cannot solve identity without solving metaphysics (and the nature of time). Unlikely we'll solve this, before creating superintelligent AI. -/- Therefore, a conservative approach to personal identity is preferable: as we don't know the nature of identity, we should preserve as much as possible and avoid Mars Teleporting unless necessary for survival. We can solve the Mars Transporter (even broken) by incorporating mind merging later, which is another conservative approach. -/- We can solve the "I don't care about my copy" problem through indexical uncertainty and by dividing "copy" into "mirror copy", "personality-copy" and "future copy". If both cyclic universe and continuity as identity are true, I will eventually become any my copy. MWI is functionally equivalent to cyclic universe, so I will become any copy in different timesteps. Therefore, we should care about parallel copies only if future copies don't exist (though in MWI future copies always exist, plus the chance to become someone else). (shrink)