Abductive arguments Flashcards
Abductive arguments
•As with inductive arguments, the aim in giving an abductive argument is to significantly raise the probability that the argument’s conclusion is true.
•However, unlike in inductive arguments, the support for the conclusion of an abductive argument is not derived from observed frequencies.
•Instead, abductive arguments have the following logical structure:
–Phenomenon Q.
–E provides the best explanation for Q.
–Therefore, E is probably true.
•The idea is that if a phenomenon occurs, then the best explanation for that phenomenon is probably true.
1. an abductive argument can be strong even if it is based on only one observed instance or phenomenon.
2. Abductive arguments are always probabilistic, because they necessarily go beyond the available evidence.
criteria of adequacy that are used to determine the strength of abductive arguments.
•The criteria used to rank the quality of eligible explanations,where “eligible” means consistent
–The best explanation is the eligible explanation that meets the criteria of adequacy better than any of its competitors.
–In an abductive argument you are only ever justified in accepting the explanation that is the best explanation in this specific sense.
–This does not mean that we are always justified in accepting the best available explanation, as we sometimes have no acceptable explanation for a phenomenon.
–The only explanation fallacy needs to be avoided. (77-78)
The Criteria of Adequacy
- Testability
- Fruitfulness
- Scope
- Simplicity
- Conservatism
- Testability
•An explanation is testable if it “yields substantive predictions that could turn out to be false” (Pendlebury, 78):
–“Consider someone’s attempting to explain why his watch has stopped by claiming that there must be a gremlinin it.
–This rules out nothing, and is consistent with anythingthat might happen to his watch.
–The idea that its battery is flat provides a much better explanation (even if it turns out to be false) because it yields at least one determinate prediction, viz., that the watch will start running again if the battery is replaced.”
- Fruitfulness
•Fruitful explanations are explanations that make previously unexpected yet accurate predictions.
–An explanation is not likely to generate novel, accurate predictions about the world simply through luck.
–Instead, an explanation that generates such predictions is likely to be, at least to some degree, accurate about the way that the world is.
•Nonetheless, plenty of good explanations do not make novel, unexpected predictions.
–Other things being equal, then, fruitful explanations are more likely to be accurate than non-fruitful explanations, but being a fruitful explanation is not necessary in order to be a good explanation
- Scope
•The scope of an explanation refers to the number of phenomena that the explanation explains.
–An explanation with large scope provides an explanation of many phenomena rather than of just one or two.
•Large scope is good for two reasons.
1.The more scope an explanation has the more it extends our understanding of the world.
2.The more scope an explanation has the more evidence there is for that explanation.
•So, other things being equal, the explanation with the greatest scope is most likely to be true.
- Simplicity
•A simple explanation is one that makes minimal assumptions.
–Ockham’s razor: “Entities should not be multiplied unnecessarily”.
–Violating Ockham’s razor involves believing that entities exist without good reason to believe that they exist.•In addition, simpler explanations require less evidence in order to be justified.
•If an explanation isn’t working, an ad hoc hypothesis can be introduced to save the explanation.
–An ad hoc hypothesis is a hypothesis that is introduced solelyin order to save an explanation or theory.
–Tinkering with explanations is often legitimate; however, ad hoc hypotheses always make explanations lesssimple.
•Other things being equal, the best explanation is the simplest explanation (the explanation that makes the fewest assumptions)
- Conservatism
•A conservative explanation is one that fits with established beliefs.
•There are two reasons that it is good for an explanation to be conservative.
1.Beliefs that conflict with our background beliefs have a lower probability of being true.
2.Conflict between beliefs entails that some of those beliefs are false.
•So, other things being equal, the best explanation is the one that fits best with our established beliefs.
•Sometimes departures from established knowledge do turn out to be correct, but we need very good reason to privilege a non-conservative explanation over a conservative explanation.
Consistency
The most basic requirement that any explanation must meet in order to be an acceptable explanation is consistency.
•Any acceptable explanation must possess two kinds of consistency:
1. internal
2. external
Obviously, if an explanation is in some way inconsistent with the state of affairs that it is supposed to explain, then it is not a good explanation of that state of affairs.
•Being consistent, though, does not in itself make an explanation good.
–For any state of affairs there are an infinite number of consistent explanations for that state of affairs and a large number of those consistent explanations will be really bad.
•However, being inconsistent does make an explanation bad and any inconsistent explanation should be rejected.
•So, for an explanation to be eligible for acceptance it must be a consistent explanation, but a consistent explanation is not necessarily an acceptable explanation
internally consistent
the explanation must be free of contradiction.
•An explanation that includes a contradiction simply does not make sense and thus must be rejected.
externally consistent
An explanation is externally consistent if it is consistent with the data that it is supposed to explain.
