It's not possible to define something by it's ability to do something else. A smoker is not smoking cigarettes, nor inhaling smoke. Whatever is responsible for consciousness (and there's plenty evidence, more than to the contrary, that is not the brain), it can not be defined by what it does. Consciousness is not my reading the words I'm writing here, not me thinking the words before writing them in a foreign language.
It's trivial to say that consciousness gives us the ability to do many things, still it escapes a definition mainly for the very fact that it does something, as opposed to everything else that falls under the umbrella of science(s), where description by attributes (e.g. the charge of the electron) sort of says what an objects says. It still escapes an ontological knowledge (we don't have the eye of God, as Putnam put it), but the electron doesn't really do anything, so we're not forced to explain something else than its properties, intrinsic or extrinsic.
It's trivial to say that consciousness gives us the ability to do many things, still it escapes a definition mainly for the very fact that it does something, as opposed to everything else that falls under the umbrella of science(s), where description by attributes (e.g. the charge of the electron) sort of says what an objects says. It still escapes an ontological knowledge (we don't have the eye of God, as Putnam put it), but the electron doesn't really do anything, so we're not forced to explain something else than its properties, intrinsic or extrinsic.