Parfit starts with the following:
"We are the animals that can both understand and respond to reasons. Facts give us reasons when they count in favour of our having some belief or desire, or acting in some way."(pg.50)
I love this opening! It summarizes a take on that which is distinctly human, that corresponds to our ability to do science as well as to consider ethics. We move from facts to beliefs and from beliefs to rationality:
"Though it is facts that give us reasons, what we can rationally want or do depends instead on our beliefs."
Facts are already not something separate from beliefs and morality; they provide us with "reasons". (pg. 50) How can a fact provide us with reasons? Only if facts are already constructed by some reasoning faculty, perhaps. Facts don't just hang out there neutrally. If they did, nothing could be done with them; they cannot be said to 'count' for or against anything.
The notion that there is this gulf between facts and values is obviously something that Parfit has struggled with/against for a long time. The only solution is that facts be defined in such a way that values can be derived from them. This is, today, a rather unpopular, and seemingly naive position; clearly Parfit is not a simpleton, so I'm going to read on!
He distinguishes wonderfully between subjective and objective theories. Subjective theories have to do with facts about us, our desires. Against that we have "objective theories, we have reasons to act in some way only when, and because, what we are doing or trying to achieve is in some way good, or worth achieving. Since these are facts about the objects of desires or aims, we can call such reasons object-given."
He then says, "We ought, I shall argue, to accept some value-based objective theory."(pg. 51)
I wish Parfit all the luck and hope he succeeds in defending an objective theory.