I feel like there's an underlying assumption/reality here that helps us: Hardware is designed for programs that are maximally efficient but also safe and correct. No one ever designs a new CPU instruction that's like "this multiplies two numbers super fast, but only if you're willing to accept undefined behavior 0.1% of the time." They only design hardware instructions that are possible to use in a safe, correct program. And so it's possible for a programming language to make progress on safety and correctness without nessarily compromising performance. The "laws of physics" as expressed in the way we build hardware allow for such a thing. That said, I wonder if other folks know stories about hardware designs that were fundamentally incorrect, and what happened to them?