Imagine that there is a room with a man, a device that can stop time outside the room, and a huge book. The huge book describes lists and lists of Chinese characters, and a good response to being shown particular sets of them. The man does not speak Chinese, nor can he grasp any meanings from their writings, but is otherwise reasonably intelligent and literate in whatever his native language is. The room also has a slot that can move letters in and out.
I take a friend who speaks one of the many Chinese languages (They're unified only by their form of writing), and I tell him, "Hey check out my Chinese-writing room. It totally understands Chinese." He doesn't believe me, but writes a message on a slip of paper. A minute later, the paper comes back out of the slot with a response. He reads the response -- it matches exactly what a reasonably intelligent Chinese-writing person would have written in response to what he wrote. "Huh, I guess your room does. Neat."
Now this is an abstraction of AI. Even if we do write AI, it will essentially work by having responses to stimuli that it applies deterministically. The program is the book, and the computer is the man. Many philosophers therefore argue that all AI can only provide the illusion of consciousness. After all, the computer (the man) doesn't understand what he's writing, but only writes what the book tells him. The book doesn't have any consciousness -- it's a thing. And the room doesn't have any consciousness, as it is a shaped chunk of plaster, wood, and metal. But I can make the argument that the system of the room, the man, and the book amounts to consciousness.
Consciousness after all is very mysterious, and we can only really observe our own. One philosopher said that it was like the only way we could know about beetles is if we each had a box, and were told that what was in the box was a beetle, and we somehow couldn't look in each other's boxes. There's a distinct possibility that different people could have different things in their boxes. Or that some boxes could even be empty.