What is the difference between “skills” and “knowledge”? Not a lot, many would argue. Sometimes, commentators even go as far as to say that skills and knowledge are so interchangeable that there is no need for the word “skills” at all.

But what does the research have to say? In his book Why Knowledge Matters, ED Hirsch (2016?) apparently supports the view that we could do away with the term “skills”. “Think how significantly our view of schooling might change if, suddenly, policymakers, instead of using the term skill, had to use the more accurate, knowledge-drenched term ‘expertise’,” he writes.

Although Hirsch’s choice to explicitly link the words “expertise” and “knowledge” is interesting, his view seems at odds with the findings of Anders Ericsson, another leading researcher in the field of expertise, who suggests (Peak: Secrets from the New Science of Expertise, Ericsson and Pool, 2016) that teachers should ask themselves how we can improve relevant skills rather than how we teach relevant knowledge.

The tension that exists between these two stances, in my view, makes it worth maintaining a distinction between “skills” and “knowledge” - if we think of the terms as interchangeable, we risk missing something.

And yet I also believe that we need to reframe how we think about knowledge and skills in order to truly understand what we mean by these words.

A good place to turn for help is the work of Stellan Ohlsson, who advocates thinking about skills as “practical knowledge”.

What exactly does he mean by this? In his 2011 book, Deep Learning: How the Mind Overrides Experience, Ohlsson explains how cognitive scientists have settled on a broad distinction between “declarative” and “practical” knowledge. Declarative knowledge is knowledge about the way the world is, while practical knowledge is knowledge about what we do; of how to perform tasks, reach goals or produce desired consequences and effects.

Although declarative knowledge and practical knowledge are interlinked, they differ in multiple ways. For example, declarative statements can be more or less accurate, while practical knowledge is neither true nor false, but rather more or less effective. In addition, practical knowledge consists of what Ohlsson calls “production rules” - three-way associations between a goal, a situation and an action.

The distinction between these two types of knowledge plays a role in how we detect errors, Ohlsson adds. “A person might possess the declarative knowledge required to judge a performance as inappropriate, incorrect or unhelpful, but nevertheless lack the practical knowledge required to perform better. This is not an exotic possibility but the normal case. The distinction between practical and declarative knowledge resolves the paradox that people can detect their own errors but it raises the question of how declarative knowledge can be represented in memory so as to serve this evaluative function,” he says.

Ultimately, while it might be tempting to view skills as a type of knowledge, or to see skills and knowledge as interchangeable, we should avoid doing away with a meaningful, evidence-based distinction. Instead, we need to keep both terms and simply learn to be clearer about what we mean by them.

Christian Bokhove is associate professor in mathematics education at the University of Southampton