Critical Thinking with Argument Maps
By Dave Kinkead, University of Queensland Critical Thinking Project
Independent and Codependent Premises
In the maps we’ve made so far, we’ve really only been mapping reasons. An argument requires more.
An argument is a connected series of statements used establish the truth of some claim.
The connected part is crucial. The maps we’ve made connect premise to conclusion but they haven’t connected premises to conclusion. This is an important distinction for analysing our reasoning.
Have a look at the following argument map …
Here, I’m offering two distinct reasons why I believe smoking sucks based on cost and health. These premises are independent of each other. Take one away (by say, removing the tax on cigarettes) and this doesn’t change the strength of the health argument.
Now have a look at this argument map …
Both premises are now working together – they are conjoined or codependent. It is a very strong inference (it is in fact valid) but if I take one of the premises away (or show it isn’t true), then my argument becomes very weak.
Codependent and independent premises can also be used together to form more complex arguments. Here, we can strength the inference in both the health & cost arguments from the first map …
To make a codependent inference in reasons.io, we need to start with two independent ones. Then, simply drag one premise onto the other. You can also edit the text of the inference by double clicking it.
Try it with the abortion argument below …
Drag ‘abortion is murder’ onto ‘murder is wrong’. Then double click ‘supports’ and change it to something more appropriate. You should end up with something like this …