Now, as you might guess, there are two extreme answers to the question, when objects compose. Never and always. These views are called mereological nihilism and mereological universalism respectively. Let us consider them in turn. According to mereological nihilism, the only objects that exist are mereological symbols, or more precisely, necessarily for any non-overlapping axis, there is an object composed of the axis if and only if, there is only one of the axis. Since tables, people, etc, would have parts if they existed, the mereological nihilist must conclude that they do not exist. Mereological nihilism isn't very intuitive, but it also faces more technical objections. An interesting challenge to mereological nihilism is the possibility of what is called mereology Atomless Gunk. Something is made of Atomless Gunk when every part of it has a proper part, that is, no part of it is such that it does not itself have any proper parts. In other words, it is not the symbol. If physics one day discovers that you and I have no symbols as proper parents, we can safely conclude that we are made of gunk. Now gunk is a problem for nihilism because only nihilism, the only material objects that exist are symbols. In not being a mereological symbol, gunk cannot exist. What's even worse, the neorealist wants to say that talk about composite objects is paraphrased into talk about the symbols that we taught composed these objects. We used to think there was a table composed of some symbols. With now the neorealist paraphrases talk about the table and to talk about symbols being arranged table wise. If it turned out that the table is gunky, then there aren't any symbols. We can no longer paraphrase, talk about the table or indeed talk about anything that is gunky. Moreover, Peter Van Inwagen has suggested his own existence is a counterexample to mereological nihilism. Since he exists and since he is not a symbol, nihilism must be wrong. Somewhat reminiscent of the [inaudible], from Inwagen's argument is that thinking cannot occur without composition. A mere collection of symbols arranged van Inwagen wise, or more generally personalize, cannot think. According mereological universalism, objects compose if and only if, they are disjoint, meaning they do not spatially overlap. The spatial locations are entirely distinct. Although these few sounds mad, most philosophers hold it. David Lewis, for instance, who by the way, raised the objection to nihilism from the possibility of gunk, states his view as follows: " I claim that mereological composition is unrestricted. Any old class of things has a mythological some. Whenever there are some things, no matter how this parrots and unrelated, there is something composed of just those things." You and I compose, you and Venus compose. The time is flea on the fattest dark in Scotland's and the Statue of Liberty in New York, compose as well. Needless to say, mereological universalism is not very intuitive. Nevertheless, there is one important reason motivating most meta-physicians to endorse it. If one doesn't say that composition always occurs, then one is forced to admit there are conceivable cases in which it is vague whether or not composition occurs. Because the very concepts that moderate answers proposed his criteria are vague. Now there is no problem whatsoever with linguistic vagueness. But many, though not all, philosophers believe not only that there is no metaphysical vagueness in the world, but even that metaphysical vagueness would be an intelligible.