  Other arguments against universals are based on the principles that there cannot be necessary connections between wholly distinct existences and that no two things can be composed of exactly the same  parts.[8]   Consider the universal methane. A molecule instantiates methane if and only if it consists of four hydrogen atoms bonded to a single carbon atom. Thus, necessarily, methane is instantiated only if carbon is instantiated. But this seems to be a necessary connection between two wholly distinct entities, the universals methane and carbon. One answer here is that methane and carbon are not wholly distinct universals since the universal carbon is a component or a part of the universal methane, the other parts being the universal hydrogen and the relational universal bonded. The problem here is that a molecule instantiates butane if and only if it consists of a chain of four carbon atoms, with the adjacent ones bonded, and the end carbon atoms are bonded to three hydrogen atoms each, while the middle carbon atoms are bonded to two hydrogen atoms each (thus the formula for butane is CH3-CH2-CH2-CH3). So, if butane is not to be necessarily connected to wholly distinct universals, one should say that carbon, hydrogen and bonded are the parts of butane. But then methane and butane are composed of exactly the same parts. So it looks as if structural universals (i.e. universals like methane and butane, such that whatever instantiates them must consist of parts instantiating certain universals and standing in certain relations to each other) offend either against the principle that there are no necessary connections between wholly distinct existences or the principle that no two entities can be composed of exactly the same parts (see Lewis 1986b for further discussion).