Book review – Understanding Ignorance: The Surprising Impact of What We Don’t Know

Ignorance has been the cause of a lot of hand-wringing in the last few years (not least by myself). There has been a disturbing trend in anti-intellectualism, coupled with a rise in conspiracy theories, misinformation and pseudoscience. I have blogged elsewhere about this topic and hope to review many of the books mentioned there in due course. In his new book Understanding Ignorance, DeNicola, professor of philosophy at Gettysburg College, Pennsylvania, starts off voicing similar concerns about an all-round increase in ignorance. But is ignorance simply a lack of knowledge?

Understanding Ignorance

Understanding Ignorance: The Surprising Impact of What We Don’t Know”, written by Daniel R. DeNicola, published by MIT Press in September 2017 (hardback, 250 pages)

Understanding Ignorance is an accessible introduction to the topic of ignorance, written for an audience beyond the philosophy community, though they will no doubt find much of interest here too. After dispelling common misconceptions regarding studying ignorance (it is not merely an absence of knowledge, so it can be studied, and doing so does not automatically negate it; we can understand the concept of ignorance, while still not understanding what we are ignorant of), and introducing the by-now famous distinction between known knowns, known unknowns, unknown unknowns, and unknown knowns popularised by Donald Rumsfeld, DeNicola structures his exploration around four metaphors. Ignorance as place, boundary, limit, and horizon.

Ignorance has been portrayed as a place in which we dwell, most famously Plato’s Allegory of the Cave, its inhabitants trapped in a state of ignorance they are ignorant of, as well as the Garden of Eden, where ignorance represented a state of blissful unawareness.

Ignorance can also be seen as a boundary, circumscribing a map of our knowledge, whether individual or collective. For each of us, the personal map of our knowledge is unique, but it has one thing in common: the area beyond one’s frontier of knowledge is gargantuan. But boundaries are not permanent, and can be pushed back through learning. Ignorance can thus encompass knowledge we have not yet learned, but also knowledge that has been forgotten again. The boundaries of knowledge are influenced by technology: with the rise of the internet, we have access to vast amounts of knowledge at the click of a few buttons. But that increasingly means we know less, we just know where and how to find it. Boundaries can also be artificially constructed. Rational ignorance arises when I choose not to study a topic as I think it’s not worth knowing. With the enormous expansion in available knowledge, people are more and more forced to choose how to allot their precious and limited time and attention. Ignorance can be drawn up as a strategic boundary when you choose you’d rather not know something. This can be as innocent as avoiding spoilers to a movie, or as influential as claiming ignorance in a criminal prosecution. And ignorance can, of course, be wilful when we purposefully avoid certain knowledge we fear will clash with notions we hold dear, something that seems on the rise today. Privacy, secrecy and confidentiality are yet other sorts of boundaries.

“[…] even if you were to read a book a day […] the roughly 30,000 books you could read in a lifetime are less than the annual publishing output”

The section of the book where DeNicola explores limits to knowledge I found some of the most interesting and humbling. Limits can be thought of, I think, as hard boundaries. These limits are temporal: bar a time machine, much of our past and future is unknowable. And even if you were to read a book a day, a feat unachievable for most, the roughly 30,000 books you could read in a lifetime are less than the annual publishing output. This reinforces just how little we can absorb in a lifetime of learning, and how vast our ignorance on a personal level remains. Limits are also biological (the limits to what our senses can observe and what the human brain can process and retain), or conceptual (statistics can help us draw up generalizations, without allowing us to ascertain the fate of an individual in a statistical population; we can merely ascribe a probability). And quantum mechanics has postulated a universe where the smallest particles behave inherently random and unpredictable, with Schrödinger’s cat being the best-known meme to arise from this. Finally, these boundaries and limits create what can be thought of as a horizon.

Woven into this, DeNicola explores the ethics of ignorance, such as the right and obligation to inform or remain ignorant of something, which applies for example to medical knowledge. And he explores its virtues and vices: though learning and curiosity treat ignorance as something to be eliminated, discretion and trust imply ignorance can have its merits. Finally, he explores how we manage our ignorance. Coping strategies used to take the form of superstitions, but have given way to inquiry and learning. We eliminate uncertainties and unpredictability (yet other forms of ignorance) through social conventions such as promises, contracts, agreements, and commitments. And we have developed a whole branch of mathematics, namely statistics, to help us predict possible outcomes and their likelihoods.

With Understanding Ignorance, DeNicola successfully and convincingly outlines the many guises of ignorance. Though this is a work of philosophy, the book is accessible enough that even an inquisitive biologist such as myself, without formal training in philosophy, can follow the arguments laid out here. As our scientific enterprise at large is aimed at increasing knowledge and pushing back ignorance, I would argue this book will be of interest across disciplines. But being a scientist is no requirement to enjoy or value this book. I think anyone inclined to introspection could take a lot away from it.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

Understanding Ignorance paperback, hardback or ebook


  1. The authorities themselves have always relied on ignorance to justify their control and income and have required ignorance out of entire classes of people whether you are talking politics, religion, economics, military, science or medicine! Cultivated ignorance is the goal of the leadership!


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