One of the core concepts of economics, and in particular conservative philosophers, is that individuals have immutable values and preferences: that not only is economic woman rational in the way she behaves, but she has worked out what she values, ranks and prefers before she interacts with the economic world. One of the great conservative intellectual triumphs – the so-called impossibility theorem – is to show that if this is true and there is no external authority enforcing choices on people, it is algebraically impossible for individuals to arrive at a commonly agreed decision that improves all their welfare. So much for liberal do-gooders! Their desire to meddle, to tax, to spend will end up improving no one’s lot.
1) The assumption is not that values and preferences are immutable. It is that they are consistent. And that is all that the word “rational” there means. If she prefers bananas to apples and apples to pears then she prefers bananas to pears. This is not a strange nor constraining assumption about human beings.
2) The impossibility theorem states no such thing. What it does say is that if preferences differ then we can’t please everyone with just the one decision. To bludgeon the point home, in a community of 50 men and 50 women we have one man who thinks rape is just great, 49 men and 50 women who think it ain’t. There is no position upon the allowance or non-allowance of rape which will meet everyone’s preference.
All of which is a bit of a problem for Willy as he’s interviewing Amartya Sen. Who makes only the entirely reasonable arguments that Willy’s understanding, as with all too many other people, of what is being said isn’t wholly correct.