For example, a man who says "science proves the doctrine of the trinity" commits a category mistake. Science can do no such thing because science only measures material things, while God is an immaterial being. To get proof for the trinity, we'll need philosophy and theology.
Virginia Postrel, the former editor of Reason Magazine, makes a common category mistake when arguing for embryonic stem cell research. In a December 2001 Wall Street Journal op-ed piece she takes aim at pro-lifers who treat
microscopic cells with no past or present consciousness, no organs or tissues, as people. A vocal minority of Americans, of course, do find compelling the argument that a fertilized egg is someone who deserves protection from harm. That view animates the anti-abortion movement and exercises considerable influence in Republican politics. But most Americans don't believe we should sacrifice the lives and well being of actual people to save cells. Human identity must rest on something more compelling than the right string of proteins in a petri dish, detectable only with high-tech equipment. We will never get a moral consensus that a single cell, or a clump of 100 cells, is a human being. That definition defies moral sense, rational argument, and several major religious traditions.As stated earlier this week, the construction analogy used by Postrel here is deeply flawed because embryos aren’t constructed piece by piece from the outside; they develop themselves from within. Her bigger problem, though, is her misuse of categories.
Can you spot her category error? Consider her claim above:
We will never get a moral consensus that a single cell, or a clump of 100 cells, is a human being. That definition defies moral sense, rational argument, and several major religious traditions.Here's the problem: She answers what is an essentially scientific question--"What kind of thing is the embryo?"--with morality, theology, and an appeal to public opinion, none of which provide the proof we need. True, science can't tell us how to value the embryo (anymore than it can tell us how to value 16 year-olds), but it can and does tell us what kind of thing the embryo is. On that point, there is little debate: From the earliest stages of development, the embryos in question are distinct, living and whole human organisms.
In short, Postrel poses a scientific question and then answers it within non-scientific categories--a clear error.