The analogy is "just because most X are caused by Y, doesn't mean you can easily test for X by looking at Y" I don't think your first point (how specific/preci

The analogy is "just because most X are caused by Y, doesn't mean you can easily test for X by looking at Y" I don't think your first point (how specific/precise are the symptoms of X) changes things, and I think your second point reinforces the analogy rather than weakens it. Most segfaults are coding errors and not OS or hardware errors ("look for horses, not zebras" / "SELECT isn't broken"). Even good medical tests have false positives and false negatives > Most autistic people are autistic because of genes they got from their parents. This is why autism often runs in families. Much less commonly, other factors can play a role, but usually in combination with genes from parents.