Subtractive Knowledge

Subtractive knowledge is the term for the idea that the most robust knowledge consists of understanding what is incorrect and what to avoid. An excerpt written by Nassim Taleb says the following:

We know a lot more what is wrong than what is right, or, phrased according to the fragile/robust classification, negative knowledge (what is wrong, what does not work) is more robust to error than positive knowledge (what is right, what works). So knowledge grows by subtraction much more than by addition - given that what we know today might turn out to be wrong but what we know to be wrong cannot turn out to be right, at least not easily.

In other words, it is easier to identify what to avoid compared to what to strive for. For example, one can more easily become rich by avoiding enormous debt, expensive divorces, and get-rich-quick schemes compared to trying to come up with the next brilliant idea.

Ali Bin Abi-Taleb (no relation to Nassim Taleb)  suggests that keeping one's distance from an ignorant person is equivalent to keeping company with a wise man.

Surrounding oneself with those of superior knowledge is a great strategy to become more intelligent. However, it may be even more crucial to avoid those who make poor decisions. As the saying goes, "If you lie down with dogs, you will get up with fleas."

Part of the reason this is true is because Black Swan events tend to be negative more often than positive. So it is more important to avoid the negative than strive for the positive. And while Black Swan events are theoretically unavoidable and unpredictable, one can build systems that are antifragile to these events, rather than trying to prevent the statistically inevitable.

Steve Jobs describes his take on this concept with the following quote:
You have to pick carefully. I'm actually as proud of the things we haven't done as the things I have done.

While there are limitations, negative knowledge (subtractive knowledge) is more robust than positive knowledge (additive knowledge) for two main reasons:

1. Negative knowledge is less prone to errors
2. Black swan events tend to be negative more often than positive; therefore, negative avoidance is more crucial than striving for the positive. (or rather even more ideal, being anitfragile to these events)

As a result, it can be more advantageous to ask "What should I avoid?" compared to "What should I do?"

-Joe