“Logic is the anatomy of thought” – John Locke
Formal logic holds that a good argument is a “sound” argument – i.e. an argument in which the truth of the propositions logically guarantees the truth of the conclusion.
By using formal logic, it is possible to infer (via deduction or induction) whether an argument is sound or not by testing whether the conclusion is made true by the supporting propositions.
A classic example of an argument based on formal logic is:
Proposition 1: “All humans are mortal”
Proposition 2: “David Beckham is human”
Conclusion: “David Beckham is mortal”
In every day life most people use “informal logic” in their reasoning and arguments. This is a much less strict version of logic that doesn’t accord to the strict rules of inference that formal logic – e.g. mathematical logic - does.
Informal logic is not so much about “truth” but more to do with “persuasion”. And as the at the core of persuasion is the idea of making it easy for your audience to “understand” you, it is of the utmost importance to ensure arguments are “well structured” and each part of the argument can easily be picked apart.
A classic format of “Informal logic” is based around a 4-tiered structure:
- Your position (I think . . .) – what you think overall
- Propositions (Because . . .) – reasons that support your position
- Arguments (As . . .) – supporting arguments that back up each of your propositions (this is also referred to as a minor “proposition”)
- Evidence (Supported by . . .) – supporting evidence to back up your arguments
So using this structure, an argument may look like this:
- Position: Liverpool are better than Everton
- Proposition: Because Liverpool are more successful on the pitch
- Argument: As Liverpool have won more cups and are higher in the league
- Evidence: Which is supported by the fact that Liverpool have won the Champions League 5 times, Everton have never won it.
Acknowledging this tiered informal logic structuring means it’s easy to formulate an argument – and equally easy for the audience to pick it apart, and judge for themselves whether they believe in the truth of each of the premises of the overall argument – i.e. the propositions, supporting arguments and supporting evidence.
Additional to the informal logic structure, influential arguers should also takes into account two further components of persuasive argument proposed in Aristotelian rhetoric:
- pathos (the convictions of the audience to whom an argument is addressed)
- ethos (the character of the arguer)
(N.B. Aristotle’s third component was logos – the logic of the argument)
Classic uses of pathos in persuasive arguments include the use of “metaphor” or “story telling”. By anchoring your propositions in your audience’s world makes them much easier to engage with.
The core to ensuring an arguer establishes ethos, is to show “moral competence” and high levels of knowledge. This can be done implicitly by the cogency and stature of your argument, or explicitly by ensuring your arguments are well supported by weighty evidence.
So to recap, borrowing off and updating Aristotle’s ancient (and ever prescient) wisdom, there are 3 rules to follow if you’re going to win arguments and influence people:
- Logos – structure your argument well, and make sure it holds true (even if it’s not true make your position at least seem true)
- Pathos – back up your position with propositions which use stories and language that chime with your audience.
- Ethos – make sure your arguments are well founded, and backed up with some juicy (believable) evidence.
