How does abductive easoning work?



I’m familiar with inductive and deductive logic, but new to abductive.

In: Other

It’s essentially reasoning to the best explanation based on limited information. Whereas deduction gives conclusions of the form *b* iff *a* and induction gives *a* if *b* for all available information, but not strictly *all* information possible (and so under available information *a* is a necessary condition for *b*), abduction gives a form *a* if *b* like induction, but in which the inferred *a* is not a necessary condition for *b*, just one possible explanation.

Technically abduction is a formal fallacy (*post hoc ergo propter hoc*), but nonetheless renders practical outputs — abduction is how you might reason based on expert knowledge and one or two incomplete data, for example; this *can* find true *a* iff *b* deductive forms of logical statements, but the veracity of such is unverifiable under the information from which this is abduced.

So for example, I know some things about politics. I observe Voter i, whom I know to be middle-class, white, and moderately educated, vote Republican. From this information my *best guess* as to i’s political ideology on a liberal-conservative spectrum would be that i is at least *not liberal-leaning* because I know of many studies that would suggest this is the case. However, I cannot rule out the possibility that Voter i simply voted Republican by mistake, or because it was raining, or any if various other explanations. I might be right (and my conclusion is quite weak anyway), but without additional information I cannot even express much confidence about whether my reasoning is likely to be correct.