Structure: There must be structure that is in common to all of a single group of objects. For example, in order to have a science of volcanoes, there must be some features that are common and essential to all volcanoes, apart from knowledge of any particular volcano. If every volcano had a completely different feature set, then once you had knowledge of one particular volcano located somewhere, you would not have knowledge of any others. So there must be structure that is common to all objects (or animals) of a set, so that knowledge of a type, and not just an individual, is possible.A better word might be "type", or "class." There must be structure or form in common to all objects of a certain type or class in order for science and knowledge to be possible.
For example, if there were no structure in common to all volcanoes, then we could never have a science of volcanoes. Each volcano would be its own different thing, and knowledge of one would not entail knowledge of all objects of that class. There would be no class or type if that were the case.
But because there is structure in common to all volcanoes, we can observe a few individual volcanoes and then have knowledge of that type of object in general, abstracted away from any particular volcano. We can observe volcanoes on Mars and have knowledge of them.
In addition, volcanoes could in principle go out of existence everywhere in the universe, and then come to exist again (say, if the universe collapsed but then rebounded in a new Big Bang). So the type/class/structure we call "volcano" exists over and above any particular volcano. It's entirely abstract, but rooted in actual reality.
What makes these things real? In many cases, matter. The structure of a volcano is not a volcano, but neither is unstructured matter. Only the structure plus the matter equals an actual volcano. So the volcano consists of matter + structure, and is thus a composite.
Note that this is closely related the actual/possible distinction we looked at in the last post. The matter considered by itself (and merely abstracted in this case) is possible, and when conjoined with a structure becomes actual.
It is also closely tied to the causal regularity we looked at [two posts ago.](http://rocketphilosophy.blogspot.com/2012/10/a-defense-of-classical-theism-2-causal.html) The regular effects that a volcano has (venting magma) is closely tied to its structure (a tube from the mantle to the surface).
- Most things of our existence are a composite of structure and matter