My interest here is in creating a model of the world. Well, not the world, but a world. I don't have the time, talent or ambition to create a rigorous simulation, and that's not what this will be. I want to make a fine distinction between a true simulation, which attempts to approximate a system by creating and changing as many variables as are necessary (or as are possible) with respect to time, and a model, which attempts to approximate a system by valuing the inputs and outputs of the system's constituent parts.
Let me give an example.
Let's say I wanted to simulate the human heart and its operation. In order to do this, I would create a system which approximated the heart by creating variables and objects based around the physical components and function of the heart. I would have an object based on a carotid artery, and within that object I would have variables which governed its operation, such as its hardness and softness, as well as how blocked it is, and so on. This kind of system is difficult to scale and is extremely error prone.
I want to avoid this as much as possible.
So let's say I want to instead create a simple model of the heart. Instead of creating variables, I create one object: the heart. Instead of worrying about what's going on inside of the heart, I worry about what goes into it and what comes out of it. Blood, yes, but more importantly, what effect it has on the other organs in the body and what effect the other organs have on the heart.
But wait! All I've done is simply increased the scale of my variables and I'm just creating a simulation all over again!
Well, not quite. See, the critical difference is that I'm not trying to simulate anything. I'm just interested in heuristics. I'm concerned with a set of inputs and a set of outputs which give us a sample of true, real-life interaction at a given state. I'm interested in the sum effect of those inputs and outputs on our well-being at some point in time. I don't care that my aorta is blocked, I don't necessarily know that my heart isn't working right, which is causing the other organs to fail, all I know for sure is that the overall effect of this is a decrease in my physical well-being.
In this model, the heart wouldn't be inherently more important than any other organ. The only difference would be what its inputs were (i.e., what other objects can affect its operation) and the fact that its outputs are everywhere in the body, meaning its operation has an effect everywhere in the body.
The beauty of a system like this is twofold. First, it greatly simplifies the amount of "special interaction" design that must be done (because the heart isn't "special"), and it allows us to reconfigure our model anytime we want. We've created a modular body which, in conjunction with other modular systems, lends us all the flexibility we need to define "what" we're made of.