IB Philosophy 1.1.2 Identity Over Time Notes

The Puzzle of Persistence

1. The question of identity over time asks what makes you the same person you were ten years ago, or even ten seconds ago.
2. As discussed in 1.1.1, personal identity raises the question of “what” we fundamentally are. Identity over time sharpens this by asking whether that identity persists across change.
3. This puzzle arises because of a fundamental tension: everything about a person seems to change (the body replaces its cells, memories fade and form, beliefs evolve, and character develops), yet we routinely speak of the same person persisting through all of this.
4. Philosophers distinguish between qualitative identity (being similar or sharing properties) and numerical identity (being literally the same individual). When we ask whether you are the same person you were a decade ago, we are asking about numerical identity, not merely whether you resemble that earlier self.
5. This distinction has huge real-world importance. Legal responsibility, the binding force of promises, and the continuity of relationships all depend on the assumption that a person at one time is literally the same individual at another time.
6. The Ship of Theseus paradox illustrates the difficulty: if every plank of a ship is gradually replaced, is it still the same ship? Analogously, if our bodies renew themselves and our memories transform, what anchors personal identity across decades?

1. The challenge is to find a criterion of personal identity (a test or standard): some feature whose presence confirms that the person now is the same person as before, and whose absence would mean the identity has broken down.
2. Without such a test, the idea of personal persistence falls apart. We could not hold people accountable for things they did in the past, honour long-term promises, or make sense of why you should care now about what happens to you in ten years.
3. This connects directly to the overarching question of what it means to be human: if we cannot establish what persists across a human life, we may struggle to articulate what distinguishes human existence from a mere sequence of disconnected events.

Locke's Psychological Continuity Account

1. As established in 1.1.1, Locke grounds personal identity in continuity of consciousness: you are the same person as your past self because you can remember those experiences as your own. The question for persistence is whether this criterion holds across an entire lifetime.
2. A major objection to Locke was raised by Thomas Reid using the “brave officer” analogy: if an old general remembers his exploits as a young officer, but cannot remember being flogged as a boy (which the young officer could recall), then by Locke's criterion the general is both identical and non-identical to the boy, a logical contradiction.
3. Derek Parfit later refined Locke’s argument by replacing strict memory identity with psychological connectedness and psychological continuity.