Derrin Nelson: My Choice #1 Martin Buber

Buber explains that "it" does not contribute, but it is experienced. What does he mean by this? If it is the thing that is providing said experience, then is it not then contributing? What does Buber mean by "contribute?" Further, he states that "those who experience do not participate." What then is participating? Is to experience passive, while participation is active? Does one have to respond to the event occuring for it to leave the realm of simply experiencing?