i would now approach the question of intelligence from a pragmatic perspective – now that I went through the grammar thing in another comment:
why do we need a definition?
for what reasons?
so, look at the stake holders.
many different fields lay claim to using the notion of intelligence
cognitive science is one of the more broad interdisciplinary fields in that it can contain not only human and animal intelligence but I can also contain artificial intelligence.
so within one existing field of study you can attempt to tackle:
psychology, neuroscience, artificial intelligence, philosophy, linguistics, and anthropology
(I mentioned linguistics in an earlier comment focusing on grammar + touched on philosophy)
I would think any general purpose, definition of intelligence that is functional, would have to serve these six different fields adequately
I said this, because it is an existing field that does use the notion of intelligence, so if a definition falls short by restricting it only to humans for example, then it fails the other portions.
so that would be my first criteria.
but I wouldn’t want to stop there. It’s worth asking “are there areas where the notion of intelligence is used that is *not included* in cognitive science?”
I don’t have an answer to that yet, but I think that’s a very important question before restricting to cog sci, which already broadened it but is it enough?