Say "Can't" With Care
By Bryan Caplan
Suppose a student fails a math test. Casual observers will often announce, “He can’t do the math.”
Or suppose a country has a horrible corruption problem. Casual observers will often announce, “The government can’t solve this corruption problem.”
In each case, I detect a casual logical fallacy.
Namely: If person X actually does Y, we can legitimately infer, “X can do Y.” But if person X does not do Y, you cannot legitimately infer that they can’t. Maybe they don’t do Y because they can’t do Y. Maybe they don’t do Y because they choose not to do Y.
What’s the real story? Figuring that out requires further investigation. Before you declare that, “X can’t do Y,” start with this simple checklist:
Step 1: See if the actor in question even tried to do Y.
Step 2: If the actor tried, examine how hard he tried.
Step 3: Look at how successful comparably-able actors are when they try their very hardest.
Thus, before you say that a kid who fails a math test “can’t” do it, you should examine (a) whether he even tried to pass, (b) if so, how hard he tried, and (c) the pass rate for comparable students who try their very hardest.
Similarly, before you say that a country “can’t” solve its corruption problem, you should examine (a) whether the country even tried to do so, (b) if so, how hard it tried, and (c) the success rate for comparable countries that try their very hardest.
You could respond, “Running such an investigation sounds awfully difficult. How do we know whether someone tried? How hard they tried? How do we find comparable actors? How do we know whether the comparable actors ‘tried their very hardest?'”
I fully agree. Knowing what someone can’t do tends to be hard. Which is precisely why you should make such claims with care.
The most egregious misuses of “can’t,” however, come when even token efforts reliably produce success. When someone says, “He can’t stop drinking,” or “He can’t stop cheating,” common sense revolts. Maybe you aren’t smart enough to pass a math test. But what skill does it take not to consume a beverage? To abstain from sex? Just don’t do it – and it is done.