Gremlins are known to live in the engines of airplanes, the spindles of hard drives, and the pipes of boiler rooms. No space within human industry has ever proven hostile enough to prevent their occupation, making them some of the hardiest lifeforms on this planet. Furthermore, they are notoriously difficult to capture, or even to spot; their presence is only ever known in hindsight, evidenced by chewed-through wires, rust-addled screws, and corrupted data.

Understanding why this is requires an understanding of the ecosystem that gremlins occupy, as well as knowledge of one of the secret laws of mechanical engineering: whenever a machine is built, whether by hand or on an assembly line, the inverse of that machine is inadvertently also built. This usually goes unnoticed, as humans tend to only see that which they themselves have invented in their creations. It is far more difficult for them to see the emergent forms that arise as a consequence, and this ignorance serves as the blind spot in which gremlins thrive.

An example of this can be found in an automobile’s engine. Human eyes can usually only see the most basic assembly: a device that ignites a mixture of fuel and air to produce motion in a series of cylinders. What they don’t see is the beast with a piston-toothed maw, which chews through steel like bubblegum over the course of tens of thousands of miles. They fail to see the corrosive oil it spits to digest rod bearings, or the manifold sparking tongues it employs to taste the subtle differences between gasolines. They can’t even detect the pulse of its heart in the rhythm of a crankshaft’s motions. When all of these processes are considered together, however, the inverse machine is clearly visible: a system which exists solely to take itself apart. The engine shares space, matter, and even motion with its nemesis, yet the two are fundamentally different beings.

Understanding this principle can allow human eyes to discern a gremlin’s anatomy within a machine, but there is more to the creature than its body alone. The gremlin also has a mind, though it is the inverse of another machine: that of the inventor’s brain.

Philosophers sometimes debate about whether or not a flintlock brain has an inverse.

Planned obsolescence can be understood as a matter of gremlin ecology.

Among androids, the inverse machine principle is a psychological matter.