Scientists have discovered a spinal fluid test that can predict with 100 percent accuracy whether people who already have memory loss are going to develop full-fledged Alzheimer’s disease. They apparently don’t know whether this test works for people with no memory problems yet, but reading between the lines of the report in the New York Times
This is truly the apple of knowledge: a test that can be given to physically and mentally healthy people in the prime of life, which can identify with perfect accuracy which ones are slowly going to lose their mental capabilities. If your first instinct is, "We should outlaw this test" or at least "we should forbid employers from discriminating on the basis of this test," congratulations—you’re a liberal. People should be judged on the basis of their actual, current abilities, not on the basis of what their spinal fluid indicates about what may happen some day. Tests can be wrong.
Fine. And now you’re going into the hospital for brain surgery. You wouldn’t be curious to know how your surgeon’s spinal fluid scores? You would be reassured if told, "Well, he’s going to have Alzheimer's, but not so you’d notice for a few years"? I doubt it.