[edanm]

That depends what you mean by intelligence.

We understand enough to build computers that win at chess, to build computers that run financial trading algorithms, to build Google.

I agree that intelligence is in some ways harder to fully define than flight, but that doesn't mean that we don't have any understanding of any parts of it.

[Falling3]

Google's definition (which is a good starting point) of intelligence: "the ability to acquire and apply knowledge and skills."

As far as I know, we have very little if anything in the way of software that accomplishes general learning (not limited to a specific domain).