 Whether this way of conceiving of mereology as a general and topic-neutral theory holds water is a question that will not be further addressed here. It will, however, be in the background of much that follows. Likewise, little will be said about the important question of whether one should countenance different (primitive) part-whole relations to hold among different kinds of entity (as urged e.g. by Sharvy 1980, McDaniel 2004, 2009, and Mellor 2006), or perhaps even among entities of the same kind (Fine 1994, 2010). Such a question will nonetheless be relevant to the assessment of certain mereological principles discussed below, whose generality may be claimed to hold only in a restricted sense, or on a limited understanding of ‘part’. For further issues concerning the alleged universality and topic-neutrality of mereology, see also Johnston (2005, 2006), Varzi (2010), Donnelly (2011), Hovda (2014), and Johansson (2015). (Some may even think that there are no parthood relations whatsoever, e.g., because there are there are no causally inert non-logical properties or relations, and parthood would be one such; for a defense of this sort of mereological anti-realism, see Cowling 2014.)