Why a little knowledge is a dangerous thing

Alexander Pope famously said

A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There shallow draughts intoxicate the brain,
And drinking largely sobers us again.

I’ve been thinking lately about why a little knowledge is often a dangerous thing, and here’s what I’ve come to.

Any complex system has many causes acting on it. Some of these are going to be more legible than others. Here I’m using “legible” in a way similar to how James Scott uses the term. As Venkatesh Rao summarizes it,

A system is legible if it is comprehensible to a calculative-rational observer looking to optimize the system from the point of view of narrow utilitarian concerns and eliminate other phenomenology. It is illegible if it serves many functions and purposes in complex ways, such that no single participant can easily comprehend the whole. The terms were coined by James Scott in Seeing Like a State.

People who have a little knowledge of a subject are only aware of some of the major causes that are acting, and probably they are aware of the most legible causes. They have an unbalanced view because they are aware of the forces pushing in one direction but not aware of other forces pushing in other directions.

A naive view may be unaware of a pair of causes in tension, and may thus have a somewhat balanced perspective. And an expert may be aware of both causes. But someone who knows about one cause but not yet about the other is unbalanced.


When I first started working at MD Anderson Cancer Center, I read a book on cancer called One Renegade Cell. After reading the first few chapters, I wondered why we’re not all dead. It’s easy to see how cancer can develop from one bad cell division and kill you a few weeks later. It’s not as easy to understand why that doesn’t usually happen. The spreading of cancer is more legible than natural defenses against cancer.

I was recently on the phone with a client who had learned enough about data deidentification to become worried. I explained that there were also reasons to not be as worried, but that they’re more complicated, less legible.

What to do

Theories are naturally biased toward causes that are amenable to theory, toward legible causes. Practical experience and empirical data tend to balance out theory by providing some insight into less legible causes.

A little knowledge is dangerous not so much because it is partial but because it is biased; it’s often partial in a particular way, such as theory lacking experience. If you spiral in on knowledge in a more balanced manner, with a combination of theory and experience, you might not be as dangerous along the way.

When theory and reality differ, the fault lies in the theory. More on that in my next post. Theory necessarily leaves out complications, and that’s what makes it useful. The art is knowing which complications can be safely ignored under which circumstances.

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2 thoughts on “Why a little knowledge is a dangerous thing

  1. Nice article John. You said it best:

    “A little knowledge is dangerous not so much because it is partial but because it is biased; it’s often partial in a particular way, such as theory lacking experience.”

    In areas like Economics, theories are heavily biased towards a small subset of legible causes that are “modelling-tractable”. So there is an expert problem here: to a freshly minted PhD armed with a large toolbox, every problem might look like an optimization problem!

  2. Dr. Cook, I’m amazed by the snippets I just read. This subject somehow reminds of something I read somewhere: ” there are those who listen,and there are those who wait to speak “. With all of the political diatribes going down today, I would like to hear a comment from you.

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