| Clue | Source | Date |
|---|---|---|
| Philosopher who said "I think, therefore I am" | The Times Specialist Sunday | 28 Jan 2024 |
| 'I think, therefore I am' | New York Times | 13 Jul 2022 |
| 'Cogito ergo sum' philosopher | Eugene Sheffer | 19 May 2018 |
| "Everything is self-evident" philosopher |