Bitcoin concept is man made purely. Bitcoin interacts with reality only bc humans devote energy to it and make space for the concept in their minds. How is bitcoin different from time? Both are abstractions? One is purely man made the other exists in the real world objectively outside man. One is useful for remembering events in time the other is only useful for making money, to the extend you can’t find greater fools bitcoin will not attract our minds attention and thus die out. Aside- for future discussion- Lyn Alden said double spend was discovered- I don’t think so since it’s part of bitcoin, also it’s not error proof.