Inference to the best explanation

Inference to the best explanation is a form of reasoning where one infers that the hypothesis, among competing hypotheses, which best explains the available data is likely true. We are guided to a particular explanation because it makes the most sense of the evidence, altlhough it will not guarantee the answer. Indeed, the hypothesis which best explains the phenomenon might not actually be the truth; nevertheless, it is a rational choice. For all we know, it may even be the best of a bad bunch: none of the competing hypotheses are good, but we choose the least bad one.

Here are some examples of IBE:

We should believe in electrons, even though they are unobservable, because their existence best explains various empirical effects we do observe.

Even though we did not see the defendant commit the crime, the left-behind evidence, such as fingerprints, best explains that he did indeed commit the crime.

My garden is wet because it rained last night whilst I slept.

Consider the last example. If we lived in a drought-stricken area and nobody else’s garden was wet, then the explanation that it had been raining might not be the best explanation. An alternative might be that an underground water pipe had burst under our garden. Or perhaps we have a neighbour whose insomniac son’s idea of fun is to throw lots of ice cubes on people’s gardens and we had recently upset that son. Or perhaps we misbehaved yesterday and angels wept over our house. Hence, our background knowledge will be influential in evaluating the competing hypotheses.

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