Merpeople live underwater, have sea-creature features, and sing. Or something that's literally made of rock and gets smarter when it's in the cold?Or are they grey-skinned aliens from another universe that can use computers and wear glasses?

Compare Our Ghouls Are Creepier, another fantasy creature with inconsistent portrayals.

The characteristic of words or phrases whose meaning is not determined with precision.

Or could they simply be beings who entertain themselves at the expense of others? So, really, you can't blame modern creators for putting their own spin on trolls.

If there is any consistency, it is that the less cute the troll, the meaner the troll, but even that tends to be subverted.

Use of one or more vague terms typically renders it impossible to establish the truth or falsity of the sentences in which they appear.

Example: 's epistemology (as understood by Schopenhauer) the notion that all of our concepts—including those involved in both science and morality—are nothing more than useful fictions.

This outlook was a significant influence on the psychological theories of Alfred Adler.

Vaihinger described the origins of his theory in The most crucial distinction among deductive arguments and the inferences upon which they rely.

In a valid argument, if the premises are true, then the conclusion must also be true.