One of my professors jokes that if he wants to see a bunch of law students pick up their pens, he'll say, "The court lays out a three-part test..." Three is perhaps the perfect number: complex enough to be more than obvious, simple enough that you might actually try to remember the parts.
Ethicist Kwame Anthony Appiah proposes one such three-part test to answer the question, "What will future generations condemn us for?" A practice we'll likely come to regret has these features:
First, people have already heard the arguments against the practice. The case against slavery didn't emerge in a blinding moment of moral clarity, for instance; it had been around for centuries. Second, defenders of the custom tend not to offer moral counterarguments but instead invoke tradition, human nature or necessity. (As in, "We've always had slaves, and how could we grow cotton without them?") And third, supporters engage in what one might call strategic ignorance, avoiding truths that might force them to face the evils in which they're complicit.
To recap, that's (a) present opposition, (b) amoral rejoinders, and (c) strategic ignorance.
That seems right to me, and I'd add a tautological fourth. The victims of any abhorrent practice - whether prisoners, animals, or the elderly - are frequently disrespected. We abuse those we consider beneath us, and in a justificatory circular twist, we diminish those whom we abuse. But anyway, Appiah offers four "contenders" for future widespread condemnation: the prison system, industrial meat production, institutionalizing the elderly, and environmental neglect. I'd add homophobia and torture (in the near-future) and xenophobia and war (in the distant).
Also, I'm addicted to
New Yorker cartoons. This one's from the January 4, 2010 issue.