9.7-9.9, Persuasion in Practical Argument Using Value-based Argumentation Frameworks

Notes taken from ‘Persuasion in Practical Argument Using Value-based Argumentation Frameworks’ by Trevor J. M. Bench-Capon (2003)

7, An example moral debate…

8, Facts in moral debate

In the discussion thus far we have assumed that all arguments relate to some value. But sometimes we need to consider matters of fact as well as opinion grounded in values…

My solution is to treat fact as if it were a value, but fact is always the value with the highest preference for all parties. Whether we prefer life to property (as in the example) is a matter of choice, but to deny facts is to depart from rational argument by resorting to wishful thinking… We will continue to refer to arguments in preferred extensions for all reasonable value orders (those which rate fact as the highest value) as objectively acceptable.

Introducing facts can bring with it uncertainty. For example, we may not know whether Carla has sufficient insulin. Thus argument (G) may be attacked by another factual argument (H) to the effect that Carla does not have ample insulin. Note (H) is itself attacked by (G)… This introduces a cycle which is single valued in that both arguments relate to fact… This means that we may get multiple preferred extensions, even if we have an ordering on values…

Now we can see that there are four possibilities for the status of an argument. Arguments may be objectively acceptable sceptically, if they appear in every preferred extension. They may be objectively acceptable credulously, if they appear in every preferred extension corresponding to some choice of facts… They may be subjectively acceptable sceptically if they appear in every preferred extension relating to some value order… Finally they may be subjectively acceptable credulously if they appear in some preferred extension.

For persuasion against this background of uncertainty, only arguments whose objective acceptance is sceptically acceptable can be made persuasive for a determined challenger. Otherwise some choice of facts and value preferences will allow him to resist the defence. While the challenger may resist persuasion by a choice of which of two uncertain alternatives to believe, the defender cannot make such a choice and hope to be persuasive. It is for this reason that the choice must be made in the problem description when setting up the… scenario… Alternatively it is necessary to resolve the factual disputes before attempting to persuade someone to accept the value-based arguments.

9, Summary…