Boolean fish logic is lacking: read on for deep thoughts on the nature of reality and the “oarfish.”

Background:

It has come to my attention that there is a type of fish called the “oarfish,” which is a weird eel-like fish (Figure 1) that I presume is named after the logical “OR” operator that is familiar to programmers and logic fans.

Fig. 1: The “oarfish” is basically a normal animal. This makes sense, because the “OR” operator is the most natural one in many ways. Using Boolean logic, we can evaluate that if there’s a fish somewhere OR there’s a different fish somewhere, then (either way), there’s a fish present. In other words:  FISH OR FISH = FISH. Seems reasonable enough!

The Issue:

Strangely, no one has catalogued the fish-related possibilities for Boolean operators besides “OR.”

Let’s see what we can figure out from first principles about a hypothetical “ANDfish,” “XORfish,” “NOTfish,” “NORfish,” etc.

Proposal:

Let’s examine the most common logical operators that could apply:

  • OR-fish: The normal fish that you’re familiar with, as discussed in Figure 1.
  • XOR-fish: The “exclusive OR” operator, which is true if A or B is individually present, but not both together. This would be a fish that exists normally in most situations, but disappears whenever two fish occupy the same space at the same time.
  • AND-fish: A fish that is only present when multiple fish intersect in the same space.
  • NOT-fish: Only true when there is NO fish. Technically a “NOT-fish” also includes everything that isn’t a fish, which is the vast majority of the universe. We will be implicitly discarding these regions.

See details in Figure 2:


Fig. 2: Boolean logic for other fish types. A) describes the type of fish interaction we’re considering. B) illustrates the odd situation of the “AND-fish,” which only exists in the overlap region between the two fish. C) shows the even stranger situation where a fish is only present in certain non-overlapping situations. Technically, the NAND-fish should also include everything in the universe that is not a fish as part of its “is it a NAND-fish” classification. D) the “NOT”-fish and “NOR”-fish are simply not present at all. These have the same downside of also technically including everything in the universe that isn’t a fish, but we’ll ignore that here

PROS: Extremely useful thought experiment that finally bridges the disciplines of Boolean logic and ichthyology.

CONS: Upon further consideration, I think the fish might actually just be called an “oarfish” because it’s sort of long and oar-shaped.

Originally published 2026-10-05.