"Complexity that works is built up out of modules that work perfectly, layered one over the other"

This quote by Kevin Kelly speaks to the value of modularity in producing intricate systems that work. By breaking down a complicated system into smaller sized, simpler elements, or modules, it ends up being simpler to understand and manage. Each module must be created to work perfectly by itself, and after that layered on top of each other to develop a bigger, more complex system. This technique allows for higher flexibility and scalability, as private modules can be modified or replaced without interrupting the whole system. It also makes it much easier to recognize and fix any problems that occur, as the problem can be isolated to a single module. By building complexity out of modules that work completely, it is possible to produce a system that is both trusted and efficient.