Spending $1 for a brand new house would feel very, very good. Spending $1,000 for a ham sandwich would feel very, very bad. Spending $19,000 for a small family car would feel, well, more or less right. But as with physical pain, fiscal pain can depend on the individual, and everyone has a different threshold.

Suffering is always hard to quantify - especially when the pain is caused by as cruel a disease as Alzheimer's. Most illnesses attack the body; Alzheimer's destroys the mind - and in the process, annihilates the very self.

Introverts listen better, they assess risks more carefully, they can be wiser managers. It's not for nothing that the Silicon Valley billionaires are so often the retiring types.

The truth, of course, is that the only necessary and sufficient condition for human beings to murder one another is the simple fact of being human.

When you're your parents' one shot at a genetic legacy, you may get to attend all the best schools, wear all the best clothes and eat all the best foods - at least relative to children in multiple-sibling households. But you also wind up with an overweening sense of your own importance.

Kids are anarchy writ large.

Toxins love to get you while you're young. Lead, mercury, secondhand smoke and sundry other environmental nasties do a lot more damage when tissue is immature, vulnerable and growing than when it's mature and comparatively fixed.