Everything can be broken down into smaller, more understandable chunks.
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Decomposition is the breaking down of a whole into its constituent parts. All systems are, by definition, composed of parts. The mere act of dividing the world at its joints facilitates understanding. Sub components can be further broken down. Practically any amount of complexity can be understood by the act of recursively breaking down, analyzing, and understanding its sub components and the interfaces between them. Ideally following the Systems Decomposition Rule of 7
Recursively breaking down complex systems is the bread and butter of IDEF0 and IDEF3, and other modeling languages.