Identity is a central concept in metaphysics concerned with what allows a person, object, or other entity to remain the same thing across time and change. Metaphysical questions about identity examine which characteristics are essential, which can change without destroying identity, and how continuity is maintained when properties, parts, or conditions are altered. Discussions of identity often connect with being, existence, substance, change, time, persistence, personal identity, and essence, making it important to theories about how entities endure and are distinguished from one another.