Could an AI be built?

It's an open question if one could be (or has already been) built.
People say that computers can't do it. I heard someone, who writes papers on such things, say last week that computers can't be conscious because they're discrete.
Now consciousness is not intelligence, but this type of argument seems weak to me.
Some say AI could never be built.
The reasons tend to be, it hasn't been done yet, so it can't be done.
Others say that their programs or robots are already intelligent.
None the less, no system yet passes the Turing test,
so I think we don't yet have an AI, but
I think we will eventually build one.