Thursday, 17 April 2014

Critical Thinking 7: Argument Reconstruction

When we are posed with an argument we must be able to dissect what we have to assess its reliability.  There is a process which we go through:

Doesn’t   It   Make   Sense   Having   It   Labelled 

Delete non-statements  -  Go through the argument and delete unneeded commands, questions, and expressions. Keep an eye on the rhetorical questions, we may need them.

Identify Conclusion(s)  -  Work out what the argument is trying to prove. Intermediate conclusions go first (C1) followed by the main conclusion (C).

Main Premise(s)  -  The main premise is normally one with an “if...then” conditional or an “all...” categorical beginning. You can see the P→Q emerging.

Supporting Premises  -  These follow the main premise either in a natural flow continuing the point or, more commonly, as a repetition of one part of the main premise.

Hidden Premises  -  You may need these to reconstruct the argument in standard form. They are implied by the other premises/conclusions.

Inference Bar  -  When writing out our argument we can often miss this out – try not to.  Inference bar goes before each conclusion.

Label Everything  -  Label each element, P1, P2, C1, C2, HP1, HP2 in order that they appear.

Consider the following argument and we can see how we reconstruct it using the above acronym.
We delete unwanted language, of which there is none. We identity the conclusion, the word therefore points us towards “Pomme is a mammal”. We highlight the main premise, since there is an ‘all...’ statement this points us towards “All cats are mammals”. Next we identify relevant secondary premises, these should either confirm an aspect of the main premise (most notable in ‘if...then’ premises) or form a link between the main premise and conclusion; for us it is “Pomme is a cat”.  Then we see if there are any hidden premises, which in this argument there isn’t. All that’s left to do it write it out formally with its inference bar and labelled components.

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