  To illustrate the basic idea: in Figure 1, the left-hand diagram  depicts a water molecule W comprising an oxygen atom o  and two hydrogen atoms h1 and h2. For the combinatorialist, “thick” particulars like the  molecule itself as well as its constituent atoms are themselves  facts: o is the fact [O,o] in which the  universal oxygen (O) is exemplified by a thin  particular   o;[43]  likewise h1 and h2. W in  turn comprises those monadic facts and the relational facts  [B,o,h1],  [B,o,h2] wherein the covalent bonding relation B holds between the oxygen atom and the two hydrogen  atoms. The structural universal Water itself, then, shares  this structure — it is, so to say, an isomorph  consisting of the monadic universals O and H and the  binary relation B, structured as indicated in the right-hand  diagram of Figure   1.[44] 