When we design a model of something, it often looks clean and simple. A couple of concepts, a few relations, and we feel we understand the whole thing. But the moment we apply that model to the real world, the complexity explodes. The complexity is not really in the abstract model itself, but in the countless concrete instances that fill it.

Take a simple example: a model of family relationships. In the abstract, this is easy to describe. You have a Person and a Relationship. The relationship can have different types: parent, child, sibling, spouse, and so on. That is basically it. A few concepts and a small set of relation types. The model is straightforward and has low complexity.

Now look at what happens when you instantiate this model in the real world. Each actual human becomes an instance of Person. Each real family connection becomes an instance of Relationship. Even in one family you quickly get many objects: parents, children, siblings, grandparents, step-parents, and more. A larger family network gives you hundreds or thousands of people and relationships.

Scale this up further. In a town, you have thousands of persons and a huge number of relationships. In a country, you have millions. In the whole world, you have billions of persons and an enormous graph of family relations between them. The abstract model has not changed at all, but the instantiated system becomes overwhelmingly complex.

So the key point is: to get a sense of real complexity, you cannot just look at the abstract model with its few concepts and relations. You have to look at the instances and objects that arise when the model is applied to reality. The real complexity is in the thousands, millions, or billions of concrete persons and relationships, not in the small, tidy schema that describes them.