Its been awhile since I read this but it seems to me you kinda got to treat it like quantum field theory. It has tremendous descriptive / predictive value so something is clearly correct but the math is impossible. Graeber's book is a bit like that and its the framework in which it is elaborated which is very hard to pin down. Is it Venetian 12th C treatment of debt or Aztec treatment of debt ? In his narrative they can occur simultaneously. So best I think to treat it gently and with respect and see what can be learned from a somewhat loopy [ at times ] narrative. A bit like art I guess.