In Dungeons and Dragons and many similar games, player characters are created with a point system, and have six attributes: strength, dexterity, constitution, intelligence, wisdom, and charisma. Each of these six attributes is represented by a number, and within an adventuring party, while one player’s character might be stronger or wiser or more charismatic, this will always be counterbalanced by a weakness somewhere else.
In the real world, people tend to sort themselves according to awesomeness. They try to hang out with people who are about as cool as they are. Your friends are about as cool as you are; their friends are about as cool as they are. As a result, if your friend introduces you to someone, that person is on average about as cool as you are, too. If you go to the best college you can get into and afford, you will mostly meet people for whom that was the best college they could get into and afford. If you go to the best party that will have you, you will on average tend to meet people for whom that was the best party that would have them.
This produces an odd effect. If you meet someone and find out that they have some significant weakness, this gives you evidence that they have some other strength, which you don’t know about; otherwise, they would’ve sorted into a different college or a different group of friends. Similarly, if you meet someone and find out that they have a particular strength, then this gives you evidence that they are weaker in some other way, for the same reason. I call this effect Conservation of Virtue.
There are three issues with the Conservation of Virtue effect. The first issue is that real people have more than six attributes, and no social dynamic is nearly so precise as a point system with everyone having exactly 75 attribute-points total. Even in a group that carefully filtered its members, you will sometimes meet people who are much more or less virtuous than the average, and if you let the Conservation of Virtue effect inform your intuition, you might fail to notice. And sometimes, you will meet people in ways that aren’t related to any filtering process, so the Conservation of Virtue effect no longer applies.
The bigger issue, though, is that this can make you believe things are tradeoffs when they really aren’t. For example, when I was younger, I noticed the cultural cliche of stupid athletes and smart but weak nerds – and, without ever raising the question to conscious awareness, came to the belief that I could make myself smarter by neglecting fitness as hard as I could. Similarly, I recall a case of someone I know complaining about good reasoners neglecting empiricism, and good empiricists neglecting complex reasoning. Sometimes, false tradeoffs even get baked into our terminology, like “Fox/Hedgehog” (aka generalist/specialist). This is closer to a true tradeoff because building generalist knowledge and building specialist knowledge are at least competing for time, but it is in fact possible to have both generalist knowledge and specialist knowledge; I have heard this referred to as being “T-shaped”.
These confusions can only manifest when things are left implicit. A statement like “I can make myself smarter by neglecting fitness really hard” could never hold up to conscious scrutiny in the presence of real understanding. By giving this effect a name, hopefully it will be easier to notice and to tell when it does and doesn’t apply.