Abstract
While “All events have a cause” is a synthetic statement making a factual claim about the world, “All effects have a cause” is analytic. When we take an event as an effect, no inference is required to deduce that it has a cause since this is what it means to be an effect. Some examples often given in the literature as examples of abduction work in the same way through semantic facts that follow from the way our beliefs represent those effects; from this we may deduce not only that it has a cause, but what that cause is.
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Notes
Nor do I wish to take any side on whether “abduction” and “inference to the best explanation” should be taken to name the same thing. Since reasoning with causal concepts does not involve the explicit elimination of hypotheses or appeal to explanatory virtues, I prefer to call it a kind of abduction, but it would be equally valid to consider a priori abduction distinct from both or even to consider it a kind of deduction, since being a priori it is deductively (materially rather than formally) valid.
It is possible that in this example the authors are misspeaking and would not deny what I will shortly be claiming, namely that there is an a priori connection between the two statements in question. I am prepared to be charitable to Walton et al. on this score. However, this is not the only place this kind of example has been put forward. Are the authors of all of these simply misspeaking?
The inference with which we are concerned and that Walton et al. take themselves to be illustrating is from “That is a bear track” to “A bear has passed this way.” I concede that the addition ‘recently’ may require an inference. I also remain agnostic about how one comes to believe “That is a bear track” to be true in the first place. A fashionable view is that there is an inference of some kind between the perceptual experience and the corresponding belief, and that this inference is abductive. Equally fashionable is the view that there is an (often non-demonstrative) inference from what people say to what we understand them as meaning. These are issues in the philosophy of perception and language respectively about which I have nothing to say. Neither is relevant to my purposes here, which is to make logical points about the nature of the illustrated inference and not about the status of the premises.
For instance, an inductive argument may authorize my use of a crystal ball for predicting the future by looking at the incidence of true predictions in the class of all predictions made using this method, but this would not mean that gazing at a crystal ball is an inductive method. It is not clear whether Fumerton fully appreciates this point.
Although they slip from this in his ensuing explanation as quoted earlier, when Walton et al. (2008, 170) refer to “tracks that look like they were made by a bear” as the data from which the conclusion is inferred they seem to be following this interpretation, insisting on a thinner perceptual content that is nevertheless transparently about a mind-independent object. The sequel will show that this makes no difference to the nature of the inference.
The conditional that says “If it walks like a duck and quacks like a duck, then it is a duck” is easily recognized as a methodological principle of reasoning rather than as an empirical generalization. It is available to any reasoner irrespective of whether they have observed ducks or even know what the word “duck” means, provided that they know what the word “like” means. This does not preclude the possibility of being radically mistaken about what a duck really is.
This abduction can be compared with the form of what Walton (2010, 168–174) calls the parascheme for argument from expert opinion. A parascheme is a quick heuristic that is meant to approximate in its judgments the complete argumentation scheme. For instance, the parascheme for argument from expert opinion is given as:
E is an expert
E asserts A
A is true
This abbreviated version is less reliable than the full argumentation scheme because it does not consider critical questions or implicit premises. But, I would add, the parascheme can be abbreviated even further as:
A is an expert opinion
A is probably true
To take A to be an expert opinion just is to take it as probably (given our current state of knowledge) true; no inference is required and we do not need to go through the list of critical questions in order to labour the obvious point that the expert must be an expert. If the expert is not an expert then A is not an expert opinion, simply because of what it means to be an expert opinion, and what this entails is that we have made a mistake about A which is not the same as committing a fallacy, as Walton (2010, 174) himself says: “[T]he notion of fallacy is generally taken in logic to represent a fallacious inference of some sort, an argument from premises to a conclusion, and not merely a false or insufficiently substantiated explicit premise in the argument.” A fallacy would be committed if, for example, we make a hasty generalization from some statistical data to the reliability of a particular person such that we mistakenly call him an expert.
The measure is called the overlap coherence measure. The coherence here is coherence between the hypothesis and the evidence rather than between the hypothesis and background information and does not consider explanatory virtues but only the same kind of probabilities that Bayes’ rule uses. Therefore, it does not confer any advantage with respect to usability and is probably no better as a description of our actual inferences than was the Bayesian. But if this measure may itself be approximated by judgments of explanatory virtue, then explanationism and Bayesianism can be friends—Bayesianism being the correct normative account and explanationism the best descriptive account.
Perhaps this is not a very strong argument, but one way to strengthen it is to draw an analogy to deduction. What deduction tells you is that if the premises are true then the conclusion must be true. But given a deductive argument, if the reasoner will not accept the conclusion then it is always open to him to reject one of the premises, or even to reject a rule of inference; our doubts about a particular pattern of reasoning may be inhibited or reinforced by our beliefs about the conclusions of other arguments instantiating the same pattern, and our doubts about a particular premise may be inhibited or reinforced by our beliefs about the conclusions of other arguments utilizing the same premise. As Quine remarked, we tend to choose the option that requires the smallest adjustment to our web of beliefs as a whole.
This is a point made by Psillos (2002, 608). According to him a method can still be ‘epistemically probative’—despite the fact that it is not more likely to be true—because it can identify, search for, and cope with, potential defeaters. This seems to constitute for Psillos another dimension of epistemic normativity, rather than, e.g., a pragmatic norm. This opens the question of what should occur when these norms come into conflict. If Psillos is right then I have the argument I require.
References
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Acknowledgment
The author would like to acknowledge financial support received from the FCT under the grant “Argumentation, Communication and Context” PTDC/FIL-FIL/110117/2009.
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Botting, D. A Priori Abduction. Argumentation 27, 167–181 (2013). https://doi.org/10.1007/s10503-012-9269-4
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DOI: https://doi.org/10.1007/s10503-012-9269-4