First introductory scenario
You are perceiving things, but the status of your perceptions is entirely indeterminate. You do not know the significance of this situation, or whether it has any. Among the things that you seem to perceive are other people, but you are unable to determine whether they have consciousness, as you seem to yourself to have. Perhaps they are automata. Or perhaps they are just hallucinatory figures in your hallucinatory dream.
Second introductory scenario
What you are perceiving seems to be a physical universe and it seems to be possible to infer certain things about the past history of this universe. It is possible to suppose that your consciousness is a by-product of physical and chemical events in your organism, and that other people are conscious in a similar way to yourself as a result of similar events in their organisms.
The human race, of which you are a part, seems to have been on the planet on which you are living for a very small part of the inferable history of the physical universe. The lifetime of the human race, and the space it occupies, is infinitesimal even in relation to the time and space that the human race is able to infer in the physical universe that surrounds it. It is inferred that there may be millions of other stars as well able to possess life-bearing planets as our sun. It is inferred that previous life-forms on this planet, such as the dinosaurs, occupied it for hundreds of millions of years.
The human race has a strong tendency to believe that what the human race regards as good and valuable is of great importance. What is important to a human being (and in what other sense could the word important have meaning) is to be determined by reference to the local consensus of belief about what is important in the social environment which surrounds that human being.
(from the forthcoming book The Corpse and the Kingdom)