At the beginning of the 20th Century, some English and American philosophers in the idealist tradition gave the following kind of argument for a moderate monism: Every individual is related to every other individual by what they called “internal relations”. The resulting web of internal relatedness implies that all things fit together to form essential parts of a single whole: the One. Although the parts of the One are in some ways distinguishable from the whole that contains them (this is a moderate monism, not the more implausible monistic insistence that there is only one thing, period1); nevertheless, the parts are dependent upon the One, due to the internal relations holding amongst them and between them and the One. The parts should therefore be regarded as “mere fragments” of something larger, since they are incapable of existing alone or outside of the whole in which they are found. Since these monists were idealists, they also had their reasons for thinking that the One is mental or mind-dependent. But some of their reasons for believing that everything stood in internal relations did not presuppose that either the relata or the relations were mental; and so this particular path from internal relations to monism need not have led directly to idealism.2 The idealists’ use of internal relations in such arguments was criticized by Moore and Russell.3 Their criticisms were effective but blunt instruments; for the most part, Russell and Moore did not examine the finer details of the idealists’ reasoning. They...