Although admitting that we don’t know the answer to the first question he still offers his guesses. He begins by distinguishing between types of animals then distinguishing between sentience and consciousness. He says that sentience is experiencing a “succession of perceptions” where consciousness sees the experiences a part of a larger whole. For example, a sentient being would have the experience of thing A then thing B then thing C where consciousness sees it as having the experience of ABC. He says humans are sentient but unconscious when they are sleepwalking.