Definition and background of informal logic
From a practical everyday perspective people argue based around an “informal logic” structure. This is a 4-part structure, involving a position, proposition, reason and evidence – as follows:
- Your position: “I think . . .”
- Your supporting proposition: “Because . . .”
- Your supporting reasons: “As . . .”
- Supporting evidence / facts: “Supported by . . .”
So, in the heat of the moment, someone arguing about President Obama might argue:
“I THINK President Obama is a great president” (POSITION)
“AS he’s a great leader” (PROPOSITION)
“BECAUSE he listens to people and commands respect” (REASON)
“SUPPORTED BY the fact that he runs monthly town hall meetings where he answers people’s questions” (FACT)
N.B. it’s often the case that the arguer will miss out parts of an argument structure collapse part of their argument structure together. For example, sometimes an arguer will leave out “supporting evidence” or on other occasions an arguer will collapse their “propositions and reasons” into one. Having said that, it’s important to try and structure your argument as definitely and well as possible, so we’d recommend using all 4 parts in structuring your arguments.
N.B.2 If you’re interested in informal logic then you’ll DEFINITELY be interested in our series of “pocket argument guides” which are based around informal logic and are fun! Check them out here . . .
Definition of how informal logic works
According to Wikipedia, Logic is the study of inference. In formal logic, the form of an argument either matches or does not match one of the forms of proper inference (or, the conclusion can be derived from the premises using accepted rules of derivation, or by some other formal method.) Informal logic, by contrast, invites us to think about the inference without formalizing it to any (great) extent.
Informal logic is often taught as (or at least importantly includes) instruction in a series of “fallacies”. These “fallacies” particularly concern modes of argumentation which are not generally covered in formal logic, (though those treated formally can also be treated informally.) These are sometimes expressed in English and sometimes in quasi-formal language, but in all expressions the “fallacies” require further work of the type described in the example above. Govier (1987) writes, “The informal fallacies, historically a central topic for informal logic, involve mistakes in reasoning which are relatively common, but neither formal nor formally characterizable in any useful way.”
