“Some systems are (or aspire to be) treelike or "arboreal" in structure, setting out first principles and deriving increasingly refined concepts from them while making an effort to avoid circularity. Others make a virtue of circularity, holding as axiomatic that the conceptual content of the first principles depends equally on those derived from it. Some systems are fragmentary by nature, consisting of several unconnected islands, each a densely interconnected clique, but with little or no connection to the rest of the conceptual archipelago.”

Different types of systems. Tree like and branching, concentric and expansive, fragmented and locally connected.