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Tutorial 5 - Multi-layer Arguments

Theory pages

Premise Objections

Some objections in multi-layer arguments are "targeted" on explicitly stated premises. They are known as premise objections.  They provide evidence that the premise is false.

 
Discussion

Consider this objection:

The Van Allen Belt is a band of radiation around the Earth. Some who hold to the conspiracy theories have suggested that the Apollo astronauts could not have survived the journey through the belt, so they cannot, therefore, have been to the Moon. However...they would not experience any immediate health problems that would prevent the journey. [6.4-6]

Here is the objection as stated, diagrammed in a simple format:

Notice that the objection works by providing evidence that the premise is false.  Thus, we can represent it more accurately as follows:

Whenever you have a premise objection, there is a simple argument made up of the objection and one of the already-stated premises.

Note that, strictly speaking, an objection to a main contention is not a premise objection. The claim it is objecting to is not a premise of another simple argument.  It is just a plain or "vanilla" objection.

 
New Concepts

A premise objection is an objection to a stated premise of another simple argument.

Inference Objections

Other times, an objection is not aimed at any stated premise; rather, it objects to the connection between the stated premises and the contention. This is an inference objection.

 
Discussion

An inference objection says, roughly, the premises may be true, but the contention doesn't follow; or, put another way, you can't infer the contention from the premises.  It provides evidence that the reason is not a good reason for the contention, even if the stated premises are true.

Example:

The American flag is seen moving in video footage recorded when the astronauts planted it on the lunar surface. Given that there is no atmosphere on the Moon, some see this as 'proof' that the scenes were filmed on earth. However the movement is the result of vibrations travelling through the solid pole and disturbing the flag. [Based on 6.1-2]

This is a very important concept, because inference objections are more common than premise objections, and so you have to understand how they work and how to map them.

 
New Concepts

An inference objection is an objection to another simple argument, providing evidence not against any stated premise but against the relationship between the stated premises and their contention

Complex Arguments

To understand how to represent inference objections in argument maps, we need to keep in mind a fundamental principle.  Every argument, no matter how complicated, is built up by combining simple arguments; and so in a fully-articulated argument map, every reason or objection must be aimed at some specific claim

In this case a single complex argument is made up of three simple arguments.  Notice how the contention of one simple argument is (almost) always a premise of another.  The only exception to this rule is the very topmost simple argument; its contention is not a premise of any other simple argument, and is called the main contention.

 
Discussion

Inference objections seem to violate this rule, for an inference objection is, by definition, not aimed at any specific premise. 

However, as we will see next, this is only because the argument is incomplete. An inference objection is not aimed at any of the currently stated premises.  It is aimed at a premise - just one that has not yet been stated.

Mapping Inference Objections

In a completed argument map, every inference objection has become an objection to some co-premise.

The main challenge in mapping the inference objection is identifying the appropriate co-premise.

 
Discussion

Another way to put this point is that every objection to an inference is also an objection to an assumption which helps connect the other premise(s) to the main contention.  That assumption can be expressed as a claim, and then the objection can be targeted on that claim.

Thus, to produce an argument map of an inference objection, follow these steps:

  1. Take the reason, and articulate all its co-premises. Follow the Rabbit and Holding Hands Rules to help you do this (see Tutorial 2).
     
  2. The inference objection will now provide evidence that one of the co-premises is false.  Identify that co-premise, and attach the objection to it.

(Note that step 2 will only apply if the inference objection is in fact relevant to the reason.  If it is completely misplaced, it might not be an objection to any co-premise.)

Example:


We saw previously that this objection was not targeted on the stated premise; it was an inference objection.

The inference objection is in fact a premise objection - though to a premise which was previously hidden.

Why do inference objections exist? Because most of the time people have not fully elaborated their arguments.  Since many premises have been left unstated, objections to those (unstated) premises have nothing to be directly targeted upon.  It will appear that they are objecting to the inference rather than to the current premises.  In a sense that is right; that is what they are doing.  However you will always find that, in a properly articulated argument map, a previously-hidden premise will come to light, and the objection will provide evidence against that premise.

Inference Rebuttals

The same general story applies to rebuttals (objections to objections).  There are premise rebuttals and inference rebuttals.

 
Discussion
   

This rebuttal is a premise rebuttal.  It provides evidence that the premise of the first objection is false.

This example from Tutorial 4 is an inference rebuttal. It doesn't deny that NASA can't produce photos of the equipment.  It says, rather, that you shouldn't infer that astronauts didn't land on the Moon. 
 
New Concepts

A premise rebuttal is an objection to an objection which provides evidence that one of the stated premises of that objection is false.

An inference rebuttal is an objection to another objection which provides evidence against the inference from the stated premises of that other objection to the falsity of its contention.  

Terminology: Premise objections vs Premise rebuttals

When should you use the term "premise objection" as opposed to "premise rebuttal"?  Easy:

  • any objection to a premise is a premise objection
  • a premise objection is also a premise rebuttal if it is a rebuttal, i.e., an objection to an objection

In short, a premise rebuttal is an objection to an objection which targets a premise.

Mapping Inference Rebuttals

In fully-articulated argument maps, inference rebuttals become premise rebuttals (i.e., they provide evidence against previously unstated premises).  

 
Discussion
   

This rebuttal is not targeted upon the first premise. It does not deny that NASA cannot produce photos of the equipment.

To map this rebuttal properly, articulate the co-premises.  The objection does deny that NASA would produce photos if the astronauts had landed. 

Summary

 
Key Points

Inference objections are mapped as objections to co-premises:

Inference rebuttals are likewise mapped as objections to co-premises.

 
New Concepts

A premise objection is an objection to a stated premise of another simple argument.

An inference objection is an objection to another simple argument, providing evidence not against any stated premise but against the relationship between the stated premises and their contention

A premise rebuttal is an objection to an objection which provides evidence that one of the stated premises of that objection is false.

An inference rebuttal is an objection to another objection which provides evidence against the inference from the stated premises of that other objection to the falsity of its contention.  

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 Last updated 28-Aug-2007