Objection: Test of the truth too weak

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Objection:

You will end up with multiple theories with equally coherent explanations of the facts. In fact, you could make up an entirely fictitious account and it could be just as coherent as a serious explanation, much like a mentally ill person can create a coherent belief system for why people are trying to kill them. Crabtree’s Bludgeon (origin obscure) states that "No set of mutually inconsistent observations can exist for which some human intellect cannot conceive a coherent explanation, however complicated." An additional criterion will then be needed to decide between them, such as Simplicity/Parsimony/ Ockams Razor i.e. the one with the fewest number of propositions.

Responses:

1. Unlikely to happen
I am not convinced that this problem would ever occur in practice, for two reasons:

• Every argument must be fully justified: to achieve full coherence, every premise must be justified either by logically valid arguments, or by facts (either Agreed Facts related to the Research Question, or Background Facts). This is a very demanding requirement, and it is not clear to me that any theory can adequately do this.
• Each theory has to explain the evidence for the competing theories: it may be easy to come up with ‘ad hoc explanations’ to explain away opposing evidence, but will be hard to fully justify these explanations and do so in a way that is consistent with the rest of the theory. For instance, a conspiracy theorist on the JFK assassination has to be careful in explaining away evidence for the Lone Gunman Theory as due to official cover-ups, since they have to have a consistent theory for how they can still trust other evidence otherwise they will be shooting themselves in the foot.

2. Simplicity is already incorporated
Although Simplicity is often talked about as a criterion for theory selection, there is actually little hard evidence for why it should be used. The strongest reason that I have seen is that the more assumptions you make, the greater the chance that one of them is wrong. But it could be argued that this is already incorporated within our truth test, since the more premises there are, the greater the risk of not being able to fully justify all of them. For instance, the more ad hoc explanations you have, the more premises you have to insert to justify when exceptions need to be made, which themselves need to be justified. The risk of incoherence goes up dramatically.

3. Theory Mapping would still be useful
If using Theory Mapping demonstrates that this is true, it will still have been useful. If it is found that there genuinely are multiple theories with equally coherent explanations, that would itself be a useful finding. Firstly, it would increase mutual respect between adherents to the different theories. Secondly, it would demonstrate the need for an additional criterion and so help build consensus in identifying one. One possible candidate could be to judge the explanations on their usefulness for making predictions. The underlying definition of truth that Theory Mapping is based upon is that truth is the accurate prediction of sense experiences, which is itself based on the fact that the fundamental reason we value ‘truth’ is to help us to cope better with reality as it presents itself to us. The explanations of facts in Theory Mapping only need to address the first-level cause of the fact. But if they can go beyond this to deeper level causes then the theory will be much more useful in predicting future sense experiences and guiding action. For instance, a conspiracy theory that traces the JFK assassination back to the Military Industrial Complex is more useful in making predictions about American society than one that simply establishes the involvement of a team of government operatives. If they both have the same level of coherence, one should therefore prefer the former. How this judgement of predictive usefulness or explanatory depth could be done in an objective manner would need to be worked out through specific cases.
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