The True Expense of Nature - BiteofanApple

The True Expense Of Nature

June 1, 2026

It's Saturday morning, and you have no plans. Perhaps your schedule happened to line up that way, perhaps the kids are gone, or maybe it's just luck. Regardless, it's glorious. You bask in the glow of a lazy morning while you decide just how you're going to spend today. In your mind you go over different ideas, considering each and its consequences.

You could go to the beach! No, too much effort. You could stay in and read a book, but it's a nice day. You could read outside. Perhaps though it's better to go for a long walk first, grab a coffee maybe? You need to grab some things at the store, and that's on the way. Eventually you arrive at a plan: walk to get coffee, read for a while at the café, then stop by the store on the way home! An excellent plan—efficient and relaxing!

What have you just done? How did you arrive at this decision? There were so many variables, a nearly infinite possibility space, yet you managed to make do. Perhaps Nature itself is not so dissimilar.

Making Decisions

When you make a decision like in the example above, you consider and explore the options you have. Implicitly you ignore certain possibilities—even with a totally free day, few people decide to spend it by committing a whimsical burglary. Instead you narrow down the options by what fits your typical habits and recent situations, and then you imagine how those possibilities might play out, weighing the consequences.

Hopefully you don't get stuck in analysis paralysis, and so, when you finally come to a decision, it's fairly optimal: taking into account your responsibilities, preferences, financial capacity, and mood.

This is a kind of optimization problem, a kind of problem that humans solve, repeatedly, every single day and similar to the kinds that are the subject of Classical Physics. In effect, you're trying to find a path through the world which minimizes the financial, personal, and societal cost. Preferred solutions are not the choices with no cost, as those are very rare, instead they're the solutions with the least cost.

In any given situation, the least costly solution should be the one that's preferred, assuming you've accounted for and weighed every type of cost.1 If we wanted to calculate the optimal solution, perhaps using some calculus, we'd need a single notion, a unit of measure, that could represent any kind of cost and then we'd need a description for how much each decision, each path you might take, might cost. But once we had that, in principle anyway, we could calculate the best option every time.

Let's call this generalized, hypothetical cost Action.

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The Principle of Least Action

The so called Principle of Least Action is a real thing and it's perhaps the most foundational concept in Physics. It's honestly a shame that it's not taught to most people who take physics in college because, while it does require some advanced mathematical techniques to actually use, the Principle of Least Action underlies all of modern Physics. It's not strictly a theory, it's an assumption: the assumption that nature always does the most optimal thing .

The French physicist, Pierre Louis Maupertuis, was the first to propose action as the currency of nature in the eighteenth century.

The trajectory of a ball being thrown.

In the time since we've seen action be used to describe every level of physical theory from Einstein's Theory of General Relativity to the Standard Model of Particle Physics. Action is truly fundamental in ways Maupertuis could never have imagined.

In truth, when considering optimal paths, action is not always minimized, but instead made stationary. Usually it is indeed a minimum, but sometimes it's more of a stable point, like the seat of a saddle or a pass between two mountains. More precisely, nature prefers paths on which the action doesn't change much in the vicinity.

Nature's Choice

In the 17th and 18th centuries nature was occasionally referred to as a proper noun. Nature was referred to, not as a phenomenon, but as a person or a god. In alchemical circles, and throughout medieval literature, Nature was sometimes depicted and referred to as a being who directly controlled the function of the natural world. In this depiction, rocks fell and water ran, not because of God's direct intervention in earthly affairs, but because he'd created Nature to do that work instead. Nature was subservient to the rules made by God, but ultimately she (and it was almost always a she) did what she could within the rules she was given.

The Mirror of the Whole of Nature<br>and the Image of Art, Robert Fludd

In modern science, it's considered uncouth to refer to Nature in this way, to personify her, as we once did. But there is a loveliness to that way of writing, and a grandeur of the tone that we've lost and one that I find quite beautiful. So I'll be...