Ink creates permanence, forcing you to be sure about what you put down– you can’t erase it.
When you write in pen, you’re signaling commitment.
Like a tattoo versus a sticker.
I used to only use pencils– and I had binders and binders full of notes in smudgy pencil.
But I found that I hardly even erased anything– though the thought of being able to do so was comforting.
And come to think of it, I hardly ever revisit my notes– do you?
Using ink is like formulating strategy, while pencil is for tactical adjustments.
You better be sure of your strategy and not be changing it every 10 minutes.
If you only have a pen, you’re forced to choose to write down only the things that you’re sure enough about that they’ll still be true in 10 years.