So maybe 1) we shouldn&#x27;t wrote systems that are tens of millions of anarchically intercoupled lines of code or 2) we should write 100 100,000  line subsystems and link them together in a rigorous way.<p>They key is then to simply avoid emergent interactions between modules&#x2F;subsystems. That&#x27;s pretty doable.<p>What doesn&#x27;t happen is that people never reason about the cost of defects. Even if they do <i>some</i> reasoning about this, they don&#x27;t apply that to other components of systems.