Mapping an argument

Dispelling the curse of knowledge


  • Clearly explaining our reasoning in writing is a challenging task
  • Argument mapping can help in organising arguments and evidence
  • Argument mapping helps draw out hidden assumptions


Presenting written arguments to others – whether in a risk assessment, legal opinion, policy proposal, scientific paper, incident report, or any other form – is one of the inescapable chores of professional life.

Unfortunately, clearly explaining our reasoning in writing is something most of us find difficult, and we don’t always achieve the effect we were after. Sometimes our audience doesn’t ‘get’ our argument. Sometimes they do get it, but spot logical holes (oops!). Sometimes they just give up, not even reading what we’ve taken so long to put together.

Fortunately, there is a technique which can help. It’s called argument mapping. This usually involves creating simple ‘maps’ or diagrams of your reasoning. However the essence of argument mapping is really just applying simple, timeless principles to organising arguments and evidence.

The roots of argument mapping are in philosophy, reaching back as far as Ancient Greek syllogisms (eg, Socrates is human; All humans are mortal; so…). For some decades, philosophy instructors have used the technique to help students develop reasoning and critical thinking skills – for which it is has been shown to be remarkably effective.

More recently, argument mapping has broken out of ‘the academy’ and made itself useful as a tool for managing complex reasoning about real-world problems.

For example, in 2015 argument mapping was introduced to biosecurity risk analysts and managers at the Australian Government Department of Agriculture and Water Resources (in Canberra) and the New Zealand Ministry of Primary Industries (in Wellington, NZ). One of their challenges is to make judgements about the level of risk involved in potential imports, such as table grapes from India. They must defend these judgements with scientific arguments and evidence, knowing that there will be intense scrutiny and probably lots of ‘flak’ from stakeholders on one side or the other (or both).

They found that argument mapping can help them take a mass of scientific detail and fit it into a framework where the key points can be succinctly stated and understood by anyone, with details slotted in underneath for anyone who wants to delve into them further.

The technique is based on applying a pattern or template called CASE (Contention, Argument, Evidence, Source). It starts with: what is your Contention? That is, what is the position you are taking or conclusion you have come to? Second, what are the general Arguments (reasons) supporting that contention? Third, each argument needs to be supported by Evidence (ie, specific information to back up the argument). And, finally, the Source shows where your evidence has come from.

For example, you might be arguing that:

(C) There is a high risk that the bacterial disease Xanthomonas campestris pv. viticola will be introduced if table grapes are imported from India, because

(A) table grapes can be infected while showing no symptoms, since

(E) the bacterium was detected on asymptomatic ‘Red Globe’ grape berries, as reported in

(S) Tostes et al 2014.

Of course, this is just a simple example. The plot thickens when we start to consider multiple distinct lines of argument and evidence; counter-considerations; and ladders of reasoning with more than four rungs. All these patterns are commonly present in real-life arguments, and if you don’t apply strong ordering principles, you can quickly end up with logical spaghetti.

One way to try to make a content-dump look like orderly reasoning is to use lots of dot points. Sometimes you’ll see a report where almost every paragraph is bulleted. This is ‘cargo cult’ logic: it has some outwards signs of organised thinking, but lacks genuine logical order.

One of the strengths of argument mapping is its ability to bring out hidden assumptions. Experts in any field tend to suffer the ‘curse of knowledge’: they’re not aware of how much others don’t know. An argument which makes perfect sense to an expert can seem, to a general audience, to be making huge leaps – if indeed it is comprehensible at all. Applying some of the simple rules of argument mapping can have an almost magical effect in exposing ideas which bridge the gaps between evidence and conclusions.

Within an organisation, one of the benefits of argument mapping is consistency. In biosecurity risk assessments, for example, the same general types of arguments tend to recur from one pest to another, with just the technical details varying from case to case. Argument mapping helps teams develop domain-specific templates which can expedite the drafting of assessments and help ensure that analysts will come up with the same kinds of arguments and draw similar conclusions from similar evidence.

One reason for the uptake of argument mapping methods is the emergence of software to support the process. For example, participants in the DAWR and MPI workshops used a new, free add-in for Microsoft Word. In most organisations Word is still the default tool for developing positions and supporting arguments, so it makes sense to create maps right there on the page. A little bit of reformatting then transforms maps into standard prose format, while retaining strong logical structure.

One of the guiding principles of argument mapping is “Don’t make me [the reader] think!” That is, present your arguments so clearly that it is nearly effortless for readers to understand what you are saying and why. When this happens, they tend to engage with the issues much more constructively.

More info: Tim van Gelder;

Note: Tim is a collaborator with CEED’s long-time friend Mark Burgman at the University of Melbourne. He welcomes all enquiries from anyone in CEED wishing to explore the potential of argument mapping in their research.

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