Not Everyone Can Code

Not everyone can debug code

Counterfactual reasoning is a technique where you assume alternative scenarios that could have happened, but did not in fact happen. You assume something is true when it is, in fact, false. A question involving a counterfactual is "What if dinosaurs had not gone extinct?" Reasoning with counterfactuals is considered an advanced cognitive skill, and it comes in quite handy when you are debugging code.

To debug effectively, you have to entertain insulting falsehoods. You must look at your own logic and ask: "Suppose this invariant I spent three days designing failed. Suppose this pointer is null, even though I checked it two lines ago. How does that world exist?" You have to temporarily decouple the state of the machine from your own intentions.

A surprising proportion of the adult population has extreme difficulty with counterfactual reasoning. They get actively frustrated or hostile when asked to reason from a premise they know to be untrue. Psychological studies (Dulit 1972, Keating 1979, Neimark 1975) estimate that roughly 20% of adults experience severe difficulty with counterfactual thinking, and another 20% experience moderate difficulty. This means that 40% or more of people are fundamentally anchored to the concrete, observable world. These people are not unintelligent; they simply possess a cognitive architecture that rejects hypothetical fictions. But because software state is entirely abstract, they will find diagnosing bugs an agonizing, borderline impossible task.

Not everyone can debug multithreaded code

Reasoning about multithreaded code is counterfactual reasoning on steroids. In a single-threaded program, you trace a single path of what happened versus what might have happened. In concurrent systems, you must simultaneously evaluate an exponential explosion of alternate histories. You have to reason about every possible interleaving of thread execution, asymmetric cache invalidations, and preemption points that could occur, even if they have never yet been observed in testing.

To the concrete mind, if a race condition does not manifest across a thousand test runs, it does not exist. To the concurrency engineer, the untested interleaving is a lurking ghost. You are not debugging a machine; you are debugging a multiverse. It requires maintaining a swarm of mutually contradictory realities in working memory all at once—a cognitive burden so unnatural that very few humans can do it well without the aid of formal models or pure architectural restraint.

Regardless of how you feel about the slogan "Everyone should learn to code", some people will have a vastly harder times than others.