Inert Knowledge: The Problem of Knowing Without Understanding


Inert knowledge is information that a person knows but doesn’t fully understand, which means that they can only recognize, express, or use it in very limited ways. For example, a student has inert knowledge if they memorize a math formula and are able to repeat it, but they don’t understand what it means or what its implications are.

Inert knowledge is a problematic and prevalent phenomenon, so it’s important to understand it. As such, in the following article you will learn more about inert knowledge, and see what you can do about it in practice.


Examples of inert knowledge

An example of inert knowledge in the context of language learning is a grammatical rule that someone memorized, without understanding what the rule actually means or knowing how to use it when speaking the language. Similarly, in the same context, inert knowledge can also consist of vocabulary words that someone memorized the definitions for, without being able to use recognize or use these words while communicating.

In addition, examples of inert knowledge appear in various other domains. Notably, this phenomenon is commonly discussed in the context of education, as in the following quote:

“Inert knowledge sits in the mind’s attic, unpacked only when specifically called for by a quiz or a direct prompt but otherwise gathering dust… Unfortunately, considerable knowledge that we would like to see used actively proves to be inert.

Students commonly learn ideas about society and self in history and social studies but make no connections to today’s events or family life. Students learn concepts in science but make little connection to the world around them. Students learn techniques in math but fail to connect them to everyday applications or to their science studies.”

— From “The Many Faces of Constructivism” (by David Perkins, in Educational Leadership, Volume 57, Issue 3, 1999)

Another example of inert knowledge, as it applies to students in educational contexts, appears in the following quote:

“… students of vocational schools have difficulties applying mathematical formulae needed for compound interest and real interest calculations. Many students do not understand the meaning of the variables and arithmetic connections involved. In many cases they simply learn the formulae by heart and apply them more or less mechanically. The selection of formulae and of specific variables often remains tied to the very surface features of the task – which may be irrelevant for solving the task.

Consequently, new surface variations result in low performance even when the deep structure of the task is the same. It has to be mentioned that the known formulae could actually be applied successfully in the habitual mechanical way. However, if the structure of the task is varied – a situation which is very likely to occur on the job – problems of knowledge acquisition as well as negative transfer are predictable.”

— From “Overcoming problems of knowledge application and transfer” (Stark et al., 2004)

Furthermore, another example of inert knowledge appears in the following story, told by Physics Nobel laureate Richard Feynman:

I was teaching a group of students who would ultimately become teachers…

I discovered a very strange phenomenon: I could ask a question, which the students would answer immediately. But the next time I would ask the question — the same subject, and the same question, as far as I could tell — they couldn’t answer it at all! For instance, one time I was talking about polarized light, and I gave them all some strips of polaroid.

Polaroid passes only light whose electric vector is in a certain direction, so I explained how you could tell which way the light is polarized from whether the polaroid is dark or light.

We first took two strips of polaroid and rotated them until they let the most light through. From doing that we could tell that the two strips were now admitting light polarized in the same direction what passed through one piece of polaroid could also pass through the other. But then I asked them how one could tell the absolute direction of polarization, for a single piece of polaroid.

They hadn’t any idea.

I knew this took a certain amount of ingenuity, so I gave them a hint: “Look at the light reflected from the bay outside.”

Nobody said anything.

Then I said, “Have you ever heard of Brewster’s Angle?”

“Yes, sir! Brewster’s Angle is the angle at which light reflected from a medium with an index of refraction is completely polarized.”

“And which way is the light polarized when it’s reflected?”

“The light is polarized perpendicular to the plane of reflection, sir.” Even now, I have to think about it; they knew it cold! They even knew the tangent of the angle equals the index!

I said, “Well?”

Still nothing. They had just told me that light reflected from a medium with an index, such as the bay outside, was polarized; they had even told me which way it was polarized.

I said, “Look at the bay outside, through the polaroid. Now turn the polaroid.”

“Ooh, it’s polarized!” they said.

After a lot of investigation, I finally figured out that the students had memorized everything, but they didn’t know what anything meant. When they heard “light that is reflected from a medium with an index,” they didn’t know that it meant a material such as water. They didn’t know that the “direction of the light” is the direction in which you see something when you’re looking at it, and so on. Everything was entirely memorized, yet nothing had been translated into meaningful words. So if I asked, “What is Brewster’s Angle?” I’m going into the computer with the right keywords. But if I say, “Look at the water,” nothing happens — they don’t have anything under “Look at the water”!

— From “Surely You’re Joking Mr. Feynman

Feynman also shared another story with a similar example of inert knowledge:

Later I attended a lecture at the engineering school. The lecture went like this, translated into English: “Two bodies. . . are considered equivalent. . . if equal torques. . . will produce. . . equal acceleration. Two bodies, are considered equivalent, if equal torques, will produce equal acceleration.” The students were all sitting there taking dictation, and when the professor repeated the sentence, they checked it to make sure they wrote it down all right. Then they wrote down the next sentence, and on and on. I was the only one who knew the professor was talking about objects with the same moment of inertia, and it was hard to figure out.

I didn’t see how they were going to learn anything from that. Here he was talking about moments of inertia, but there was no discussion about how hard it is to push a door open when you put heavy weights on the outside, compared to when you put them near the hinge — nothing!

After the lecture, I talked to a student: “You take all those notes what do you do with them?”

“Oh, we study them,” he says. “We’ll have an exam.”

“What will the exam be like?”

“Very easy. I can tell you now one of the questions.” He looks at his notebook and says, ” ‘When are two bodies equivalent?’ And the answer is, ‘Two bodies are considered equivalent if equal torques will produce equal acceleration.'” So, you see, they could pass the examinations, and “learn” all this stuff, and not know anything at all, except what they had memorized.

— From “Surely You’re Joking Mr. Feynman


When is knowledge considered inert

The key reason that knowledge is considered inert is that a person only knows it, but doesn’t actually understand it, and therefore can’t do much with it. Accordingly, when someone’s knowledge is inert, that could mean that:

  • They don’t understand what it means, what its implications are, or how it connects to other relevant knowledge.
  • They can’t recognize it when it’s presented in ways or contexts that are even slightly different than they’re used to.
  • They don’t know how to apply it in practice, or don’t know how to do so when even minor adjustments are necessary.

For example, in the context of physics, inert knowledge can involve being able to repeat a formula verbatim, without understanding what it means, without being able to recognize it when it’s phrased a different way than what one is used to, and without knowing how to use it.

This conceptualization of inert knowledge has been discussed by many scholars and educators. The following is a key example of this, from the book that popularized this concept:

“In training a child to activity of thought, above all things we must beware of what I will call ‘inert ideas’⁠—that is to say, ideas that are merely received into the mind without being utilised, or tested, or thrown into fresh combinations.”

— From “The Aims of Education“, by Alfred North Whitehead (1929)

Another example of this is the following:

“You need facts to make sense; they are the basis for understanding, but they are never enough. Inertia as pathology describes those states of mind where people come to know something but simply can’t go beyond the facts, can’t synthesize them, think with them, or apply them in another situation.”

⁠— From “Taking Learning Seriously” by Lee S. Shulman (1999)

In addition, when conceptualizing inert knowledge, a useful framework to use is Bloom’s taxonomy, which describes six main types of abilities in the context of educational goals (presented here based on the revised version of the taxonomy):

  1. Remembering. This involves “Retrieving relevant knowledge from long-term memory”, by performing actions such as recalling and recognizing.
  2. Understanding. This involves “Determining the meaning of instructional messages, including oral, written, and graphic communication”, by performing actions such as interpreting, exemplifying, classifying, summarizing, inferring, comparing, and explaining.
  3. Applying. This involves “Carrying out or using a procedure in a given situation”, by performing actions such as executing and implementing.
  4. Analyzing. This involves “Breaking material into its constituent parts and detecting how the parts relate to one another and to an overall structure or purpose”, by performing actions such as differentiating, organizing, and attributing.
  5. Evaluating. This involves “Making judgments based on criteria and standards”, by performing actions such as checking and critiquing.
  6. Creating. This involves “Putting elements together to form a novel, coherent whole or make an original product”, by performing actions such as generating, planning, and producing.

In accordance with this, inert knowledge can be viewed as knowledge that a person can only use for basic activities, that primarily involve remembering, which is the lowest level of abilities in Bloom’s taxonomy. Furthermore, even within this level, inert knowledge can sometimes only be used to a limited degree; for example, someone might be able to recognize material that is part of their inert knowledge, but only as long as the material is presented exactly as they know it.

Conversely, based on this taxonomy, active (i.e., non-inert) knowledge can be viewed as knowledge that a person can also use in more sophisticated ways, which involve higher levels of abilities and thinking, such as understanding, applying, and creating.

Moreover, based on this taxonomy, it is possible to view the distinction between inert and active knowledge as involving a spectrum, rather than a binary status. This means that rather than simply classifying knowledge as either inert or active, it is possible to classify the degree to which it is inert or active, based on the type of actions that a person can perform with it. For example, knowledge that someone can understand and apply can be considered more active than knowledge that someone can only remember, but less active than knowledge that someone can also analyze and evaluate.


Types of knowledge

The revised version of Bloom’s taxonomy, which can be used in the classification of inert knowledge, deals with two dimensions of learning:

  • The cognitive process dimension. This involves the operations that people perform with different types of knowledge.
  • The knowledge dimension. This involves the different types of knowledge that people have.

As shown earlier, inert knowledge can be classified using the cognitive process dimension, based on the operations that a person can perform with it. However, when discussing the concept of inert knowledge, it can also be beneficial to understand the four different types of knowledge included in the taxonomy, which are described as follows:

  • Factual knowledge. This involves knowledge of “The basic elements that students must know to be acquainted with a discipline or solve problems in it”. For example, this includes knowledge of terminology and knowledge of specific details and elements.
  • Conceptual knowledge. This involves knowledge of “The interrelationships among the basic elements within a larger structure that enable them to function together”. For example, this includes knowledge of classifications and categories; knowledge of principles and generalizations; and knowledge of theories, models, and structures.
  • Procedural knowledge. This involves “How to do something; methods of inquiry, and criteria for using skills, algorithms, techniques, and methods”. For example, this includes knowledge of subject-specific skills and algorithms; knowledge of subject-specific techniques and methods; and knowledge of criteria for determining when to use appropriate procedures.
  • Metacognitive knowledge. This involves “Knowledge of cognition in general as well as awareness and knowledge of one’s own cognition”. For example, this includes strategic knowledge; knowledge about cognitive tasks, including appropriate contextual and conditional knowledge; and self-knowledge.

Any of these types of knowledge can be inert, although inert knowledge is most commonly discussed in the context of factual knowledge.


How to identify inert knowledge

You can identify inert knowledge in yourself and in others by checking what kind of operations the person who has the knowledge can perform with regard to it. For example, if you’re wondering whether your knowledge of a certain statistical concept is inert or not, you can check whether you can summarize what it means, provide relevant examples of how it can be implemented, and explain how it relates to similar concepts. If you can’t do any of these things, and can only repeat the basic formulation of the concept, then that indicates that your knowledge is likely inert.

To help determine whether knowledge is inert, you can ask relevant guiding questions, such as the following:

  • How well do you recognize it? For example, can you identify it when it’s presented in a different context that you’re used to?
  • How well do you understand it? For example, can you explain it in an intuitive way to someone who lacks expertise in the relevant field?
  • How well can you apply it? For example, can you implement it in various real-world situations?
  • How well can you analyze it? For example, how well can you connect it with other relevant concepts?
  • How well can you evaluate it? For example, can you identify potential issues with this knowledge?
  • How well can you create with it? For example, can you use this knowledge in order to produce something new?

Some of these questions will require modifications based on various factors, such as the type of knowledge in question, so you should simply view them as general examples of the kind of questions you should ask.

Finally, keep in mind that it can be beneficial to determine how inert and how active knowledge is, rather than just determining whether it’s strictly inert or strictly active. For example, if you can explain a certain concept in a limited way and implement it in a limited range of contexts, then it will not necessarily be right to say that the knowledge is entirely inert, but it will be valuable to notice that it might be inert in some aspects, meaning that there are substantial limitations to how you can use it.


How to avoid and transform inert knowledge

“…theoretical ideas should always find important applications within the pupil’s curriculum. This is not an easy doctrine to apply, but a very hard one. It contains within itself the problem of keeping knowledge alive, of preventing it from becoming inert, which is the central problem of all education.”

— From “The Aims of Education” by Alfred North Whitehead

When it comes to solving the problem of inert knowledge, there are three main goals:

  • Transforming inert knowledge into active knowledge.
  • Preventing active knowledge from becoming inert.
  • Avoiding the development of inert knowledge in the first place.

There are various ways to achieve this. Most notably, the key is to ensure that engagement with the relevant knowledge is deep rather than shallow, meaning that it requires more than simple memorization and limited usage within narrow contexts. This means, for example, that if you want to develop active knowledge of a physics formula, then you should not only memorize it, but also do other things with it, such as apply it in many contexts, explain its meaning, and show how it relates to other formulas.

To do this successfully, it can help to consider the various cognitive processes outlined in Bloom’s taxonomy, and make sure that the relevant knowledge is used to engage in as many of them as possible or necessary. Specifically, this can involve the following:

  • Remembering the information, and being able to recognize it even when it appears in different forms or contexts than what one is used to.
  • Understanding the information, by doing things such as interpreting it, generating relevant examples of it, summarizing it, and explaining it.
  • Applying the information, by doing things such as implementing it in real-world scenarios.
  • Analyzing the information, by doing things such as organizing it into different parts and understanding how these parts relate to each other.
  • Evaluating the information, by doing things such as critiquing it and making relevant judgments.
  • Creating new things based on the information, for example by connecting multiple pieces of knowledge to form a new theory.

Overall, to solve the problem of inert knowledge, you need to activate already inert knowledge, prevent active knowledge from becoming inert, and avoid the development of inert knowledge in the first place. To achieve this, you should ensure that engagement with the relevant knowledge is deep, meaning that it involves a range of complex cognitive processes, such as application, analysis, and evaluation.


Knowledge-telling and knowledge-building

When it comes to avoiding and transforming inert knowledge, a useful distinction to understand is the one between knowledge-telling and knowledge-building:

  • Knowledge-telling involves relatively shallow engagement with study material, generally by only going over it with little analysis or reflection. An example of knowledge-telling is reading material repeatedly to memorize it, or sitting in a lecture where you’re expected to do nothing but listen and write down what you’re told.
  • Knowledge-building involves relatively deep engagement with study material, for example by analyzing it in-depth and examining it from various angles. Knowledge-building can be promoted by the use of various techniques, such as highlighting key points in the material, drawing connections between different parts of the material, and asking open-ended questions about the material.

Inert knowledge is associated with a focus on knowledge-telling, and to avoid it, you should focus on knowledge-building instead.


Avoiding inert knowledge in education

“Education with inert ideas is not only useless: it is, above all things, harmful—Corruptio optimi, pessima [the corruption of the best is the worst of all].”

— From “The Aims of Education” by Alfred North Whitehead

The guidelines and techniques that were outlined in the previous sub-sections can be beneficial both for avoiding inert knowledge in your own learning, and for avoiding it while teaching others. However, additional considerations can come into play with regard to this in certain contexts, and particularly in formal education.

A notable source on the topic is the book that popularized the concept of inert knowledge, which says the following:

Let us now ask how in our system of education we are to guard against this mental dryrot. We enunciate two educational commandments, “Do not teach too many subjects,” and again, “What you teach, teach thoroughly.”

The result of teaching small parts of a large number of subjects is the passive reception of disconnected ideas, not illumined with any spark of vitality. Let the main ideas which are introduced into a child’s education be few and important, and let them be thrown into every combination possible. The child should make them his own, and should understand their application here and now in the circumstances of his actual life. From the very beginning of his education, the child should experience the joy of discovery. The discovery which he has to make, is that general ideas give an understanding of that stream of events which pours through his life, which is his life.

By understanding I mean more than a mere logical analysis, though that is included. I mean “understanding” in the sense in which it is used in the French proverb, “To understand all, is to forgive all. ” Pedants sneer at an education which is useful. But if education is not useful, what is it? Is it a talent, to be hidden away in a napkin? Of course, education should be useful, whatever your aim in life. It was useful to Saint Augustine and it was useful to Napoleon. It is useful, because understanding is useful.

⁠— From “The Aims of Education” by Alfred North Whitehead

Furthermore, similar sentiments have been expressed by others. For example:

“Since the ultimate purpose of any education is to help students to go well beyond the limitations of any formal instruction, the epidemiology of inertia should comprise a serious domain of institutional inquiry for higher education.”

⁠— From “Taking Learning Seriously” by Lee S. Shulman (1999)

In general, there are two main approaches you can use in education to avoid inert knowledge:

  • Teach in a way that encourages the development of active knowledge. For example, when teaching students about a certain concept, help them truly understand what it means, how it relates to other things that they know, and how they can use this information in practice. Furthermore, you can use various other techniques and tools, such as simulation of relevant scenarios, to help students move from relatively passive reproduction of inert knowledge to more active interaction with and production of knowledge.
  • Encourage people to learn in a way that encourages the development of active knowledge. For example, you can tell students about the concept of inert knowledge, explain to them why it’s problematic, and encourage them to ask themselves relevant guiding questions as they learn new material, to ensure that new knowledge that they develop is active.

In addition, you should do what you can to ensure that students’ incentives encourage them to develop active knowledge. For example, this means that if you use tests as part of your teaching and assessment process, then those tests should require active—rather than passive—knowledge.


Associated conceptualization and techniques

In some cases, the concept of inert knowledge is conceptualized in a narrower sense than the one described here. Notably, a common conceptualization is described as follows:

“Laboratory studies often use a two-stage (A-B) transfer paradigm in which participants receive: (A) one or more cases to evaluate under a study task, and then (B) a new problem that (unbeknownst to the participant) can be solved using the relational principle presented in (A). Findings based on this research show that people struggle—they typically fail to access stored analogs (even those just encountered) to solve new problems if the cue and source cases lack surface similarity…

This broad-based failure to access the relevant content from memory is referred to as the inert knowledge problem…”

— From “Sorting out the problem of inert knowledge: Category construction to promote spontaneous transfer” (Kurtz & Honke, 2020)

There are various techniques that can be used to solve the problem of inert knowledge in this and similar context. They generally involve examining specific examples of things on a conceptual and abstract level, especially across different domains, in order to improve people’s understanding of them. This can be done using various techniques, such as category constructionrelational labeling, and analogical abstraction.


Summary and conclusions

  • Inert knowledge is information that a person knows but doesn’t fully understand, which means that they can only recognize, express, or use it in very limited ways.
  • For example, a student has inert knowledge if they memorize a math formula and are able to repeat it, but they don’t understand what it means or what its implications are.
  • To transform existing inert knowledge into active knowledge and avoid developing inert knowledge in the first place, you should engage with relevant information in a deep manner, meaning that instead of simply memorizing it you should try to understand, apply, analyze, and evaluate it, as well as use it to create new things.
  • To achieve this, you can do things such as examine examples of the knowledge in various contexts, summarize the knowledge, explain it to others, use it in practice, critique it, and draw connections between it and other knowledge.
  • To help others develop active knowledge, you can also use these techniques in your teaching, or encourage others to use these techniques; when doing this in educational contexts, you may also benefit from doing other things, such as ensuring that students have enough time to engage with the material in-depth, and ensuring that students are incentivized to develop active knowledge.