First and foremost, I do it for me. The memex I’ve created by thinking about and then describing every interesting thing I’ve encountered is hugely important for how I understand the world. It’s the raw material of every novel, article, story and speech I write.
And I do it for the causes I believe in. There’s stuff in this world I want to change for the better. Explaining what I think is wrong, and how it can be improved, is the best way I know for nudging it in a direction I want to see it move.
I also like your suggestion that it is your ‘outboard brain’.
I go through my old posts every day. I know that much – most? – of them are not for the ages. But some of them are good. Some, I think, are great. They define who I am. They’re my outboard brain.
The question I wonder is how your purpose has changed over time? Clearly your process with Blogger is different than what you do now, is there anything beyond that?