 Whether this issue is best approached by considering if and how tropes can make up or ground the existence of what me might call ‘ordinary’ objects, or if it is better to concentrate instead on the world’s simplest, most fundamental, objects—like those you find discussed in e.g., fundamental physics—is another issue on which trope theorists disagree. Campbell thinks we should concentrate on the latter sort of object. In particular, he thinks we should concentrate on objects that have no other objects as parts, as that way we avoid confusing ‘substantial’ complexity (and unity) with the—here relevant—qualitative one. Robb (2005) and McDaniel (2001) disagree. This may in part be due to the fact that they both (cf. also Paul 2002, 2017) think that objects are mereologically composed both on the level of their substantial parts and on the level of their  qualitative—trope—parts.[31]