Software is a temporary garden whose fate is inextricably intertwined with its gardeners. Beyond that, software is a theory. It’s a theory about a particular solution to a problem. Like the proverbial garden, it is composed of a microscopic ecosystem of artefacts, each of whom has to be treated like a living thing. The gardener develops a sense of how the parts connect and affect each other, what makes them thrive, what kills them off, and how you prompt them to grow. The software project and its programmers are an indivisible and organic entity that our industry treats like a toy model made of easily replaceable lego blocks. They believe a software project and its developers can be broken apart and reassembled without dying.
What keeps the software alive are the programmers who have an accurate mental model (theory) of how it is built and works. That mental model can only be learned by having worked on the project while it grew or by working alongside somebody who did, who can help you absorb the theory. Replace enough of the programmers, and their mental models become disconnected from the reality of the code, and the code dies. That dead code can only be replaced by new code that has been ‘grown’ by the current programmers.
Having worked on large and complex codebases that were written before my tenure began, this quote cannot be understated as it relates to software engineering! Being able to accurately grok, review, fix, observe, or test a software system and build an accurate mental is an invaluable skill. Definitely more important than being able to invert a binary tree.