Ben Platts-Mills in Psyche:
When you wake up in the morning, how do you know who you are? You might say something like: ‘Because I remember.’ A perfectly good answer, and one with a venerable history. The English philosopher John Locke, for example, considered memory to be the foundation of identity. ‘Consciousness always accompanies thinking,’ he wrote in 1694. ‘And as far as this consciousness can be extended backwards to any past Action or Thought, so far reaches the Identity of that Person.’
For most of us, the question of where identity comes from doesn’t have much bearing on day-to-day life. We don’t have to try to remember who we are; it just happens. But for the growing number of people who survive brain injury every year, it can be a different story. If you survive an accident or an illness that limits your ability to form new memories, leaving you with what’s called ‘anterograde amnesia’, you might be forced to look elsewhere for your sense of self.