[bdowling]

> existing things with maybe a new twist somewhere.

To be valid, a claim must be novel (new) and non-obvious over the prior art. So there absolutely must be a new twist somewhere.

[adrianN]

I can still build a machine entirely from off-the shelf parts, connecting them exactly in the ways they're built to connect to each other, and claim to have invented it.

[bdowling]

If the resulting combination is a machine that is useful, new, and non-obvious, then I'd call that an invention.