How Many Things Are There?

The core finding is that the total number of “things” is dominated by what minds can imagine—not by what exists in the physical universe. Once “thing” is defined broadly enough to include real objects, abstract ideas, and even impossible concepts, the count stops being limited by matter and instead becomes limited by how many thoughts could possibly be generated before the universe runs out of usable energy.

The argument starts with a reality check using scale. Even throwing all 7.159 billion humans into the Grand Canyon wouldn’t fill it; humanity is physically tiny compared with Earth’s vastness. That perspective is reinforced with everyday production and inventory examples: people produce roughly one to two litres of spit over a lifetime, 560 billion Lego parts have been manufactured, and Earth’s sand grains are estimated at about 7.5 × 10^18. Those comparisons set up the central question: how many things are there in total?

A key move follows: “thing” is defined as anything that can be thought about or talked about. That includes physical items (yellow things, concrete, dogs), imaginary and impossible entities, and even events and future-looking concepts. The immediate temptation is to declare the answer infinite because “thing” is vague. The counter is to avoid double counting and to separate physical existence from mental representation.

For physical things, the limiting factor is not just what exists, but what can be observed. The universe’s size is uncertain—possibly infinite, possibly finite, possibly with other universes—but the discussion narrows to the observable universe. Its future visibility limit is estimated at about 62 billion light-years in any direction, containing on average roughly 10^80 elementary particles. Under the working assumption that these are the smallest real constituents, everything else—water, planets, saxophones—can be treated as arrangements of those same particles, meaning the “physical inventory” is effectively bounded by the number of elementary units (or, more cautiously, by the maximum number of smallest measurable chunks).

To guard against the possibility that today’s “elementary” particles are composite, the count is pushed to an extreme: the smallest measurable scale, a Planck volume. About 10^183 such volumes could fit within the observable universe, giving a conservative upper bound on how many distinct physical “things” could be packed into reality.

Mental things are then treated differently. Possible thoughts are argued to be effectively unbounded in principle (numbers and math don’t show an obvious largest imaginable value), but the number of thoughts that can actually be generated is constrained by physics: available energy and computation time. Using Bremermann’s Limit (1.36 × 10^50 bits per second per kilogram) and an estimate of the observable universe’s mass (3.4 × 10^60 kilograms), the maximum computable information is calculated. With roughly 3.154 × 10^116 seconds from the beginning of time to heat death, and assuming each “thought” takes about a sentence’s worth of information (~800 bits), the total number of thoughts that could ever be thought comes out to about 1.458 × 10^227.

The punchline is comparative: within the observable universe, the number of possible thoughts dwarfs the number of physical things. Even when the two totals are combined, physical counts barely change the overall total. In that sense, the universe’s inventory is less about matter than about mind—“when it comes to every thing in the universe,” the thought count is what matters most.