Sensing Physical Necessity: An Exercise In Naturalism

A philosophical thought experiment by user Algon has captured significant attention on the rationalist forum LessWrong. The post, titled 'Sensing Physical Necessity: An Exercise In Naturalism,' documents the author's attempt to introspectively identify the distinct sensory or cognitive 'feeling' that accompanies the judgment that something is physically impossible, as opposed to merely difficult or embarrassing. The exercise begins with mundane physical obstacles, like a column or a tree, and escalates to imagining jumping between buildings, probing for a subtle internal signal that says 'you can't do that.'

The investigation takes a compelling turn when it shifts from physical to cognitive tasks, specifically software engineering. The author contrasts the feeling of attempting to reverse-engineer an old contractor's complex codebase in one hour with doing Karatsuba multiplication in C within the same timeframe. The breakthrough insight is that framing these challenges as a bet with odds—like a friend offering 1/5 odds or a contractor offering 1/30 odds—serves as a more reliable and faster heuristic for uncovering one's true, often subconscious, assessment of impossibility. The mention of using tools like 'Claude Code' to tackle such tasks hints at how modern AI is reshaping our perception of what is computationally feasible.