In philosophy, the issue of personal identity concerns several loosely related issues, in particular persistence, change, sameness, and time. Personal identity is the distinct personality of an individual and is concerned with the persisting entity particular to a given individual. The personal identity structure appears to preserve itself from the previous version in time when it is modified. It is the individual characteristics arising from personality by which a person is recognized or known.Generally, it is the unique numerical identity of persons through time. That is to say, the necessary and sufficient conditions under which a person at one time and a person at another time can be said to be the same person, persisting through time. In the modern philosophy of mind, this concept of personal identity is sometimes referred to as the diachronic problem of personal identity. The synchronic problem is grounded in the question of what features or traits characterize a given person at one time.Identity is an issue for both continental philosophy and analytic philosophy. A question in continental philosophy is in what sense can the contemporary conception of identity be maintained, while many prior propositions, postulates, and presuppositions about the world are different.