I can wear your cuff-links and you can borrow my cologne. But my thought is my thought and your thought is your thought. And my thought is closer to me than both cuff-link and cologne.
There is nothing else on the planet that is so appropriated, taken for granted as belonging to ‘Me’, as ‘My Thoughts’. That’s why it is so real.
As long as I have my thoughts, I have me.
[Are you sure it is your thought you are thinking right now?]
What is it that I am absolutely certain about? The first Moon-Landing was actually faked in Utah. Cream-Pie widens the arteries. My mother really loves me. Maybe; maybe not.
But I don’t have these invidious doubts about whose thoughts are bouncing around in my head. The thoughts in my head are my thoughts. What happens in my mind is mine! mine! mine!
So it was that René Descartes, founder of Cartesian method and Father of Western Academic Philosophy wrote:
‘Thinking. At last I have discovered it- Thought. This alone is inseparable from me.’
Cogito ergo sum.
[Descartes’ rationale was more nuanced than the standard academic bumper-sticker interpretation. We’ll get to it later in his less-known letters.]