John Rawls, the brilliant 20th-century philosopher, argued for a society that seems fair if we consider it from behind a “veil of ignorance” — meaning we don’t know whether we’ll be born to an investment banker or a teenage mom, in a leafy suburb or a gang-ridden inner city, healthy or disabled, smart or struggling, privileged or disadvantaged. That’s a shrewd analytical tool — and who among us would argue for food stamp cuts if we thought we might be among the hungry children?

As we celebrate Thanksgiving, let’s remember that the difference between being surrounded by a loving family or being homeless on the street is determined not just by our own level of virtue or self-discipline, but also by an inextricable mix of luck, biography, brain chemistry and genetics.

For those who are well-off, it may be easier to castigate the irresponsibility of the poor than to recognize that success in life is a reflection not only of enterprise and willpower, but also of random chance and early upbringing.