 Although it is also a form of underdetermination, what we described in Section 1 above as contrastive underdetermination raises fundamentally different issues from the holist variety considered in Section 2 (Bonk 2008 is a book-length treatment of many of these issues). This is clearly evident in Duhem’s original writings concerning so-called crucial experiments, where he seeks to show that even when we explicitly suspend any concerns about holist underdetermination, the contrastive variety remains an obstacle to our discovery of truth in theoretical science: