Reasoning to the best explanation is a method of reasoning where you look at the available evidence and ask:
“What explanation best accounts for all of the evidence?”
It is often called inference to the best explanation (IBE), or abductive reasoning.
Suppose you wake up and find:
The ground is wet.
The streets are wet.
There are puddles everywhere.
The weather forecast predicted rain.
You could propose several explanations:
Someone sprayed all the streets with a hose.
A water main broke.
It rained.
The evidence doesn’t logically prove that it rained. But rain is the best explanation because it explains the evidence with fewer additional assumptions.
So the reasoning is:
Evidence → possible explanations → compare explanations → choose the explanation that best accounts for the evidence.
Several factors are normally considered:
| Criterion | Question |
|---|---|
| Explanatory scope | How much of the evidence does it explain? |
| Explanatory power | How well does it explain the evidence? |
| Simplicity | Does it require unnecessary assumptions? |
| Consistency | Does it fit with other things we know? |
| Predictive ability | Does it make successful predictions? |
| Ad hoc assumptions | Does it require special excuses to save itself? |
| Plausibility | Is the explanation itself reasonable given background knowledge? |
Deduction:
All humans are mortal.
Socrates is a human.
Therefore, Socrates is mortal.
If the premises are true, the conclusion must be true.
Inference to the best explanation:
The ground is wet.
The streets are wet.
There are puddles.
The forecast predicted rain.
Therefore, it probably rained.
The conclusion isn't guaranteed. It is the best explanation of the evidence.
IBE asks something slightly different from:
“How probable is this event?”
Instead, it asks:
“Which hypothesis, if true, would make the evidence make the most sense?”
For example, imagine finding a series of footprints in fresh snow. You might consider:
A person walked through the snow.
An animal made them.
They were produced artificially.
You compare how well each hypothesis explains the pattern, size, spacing, direction, etc. of the footprints.
The goal isn't merely to find something that is possible. Almost anything can be made possible with enough assumptions. The goal is to find the hypothesis that provides the most satisfactory overall explanation.
IBE does not mean:
“Whatever explanation seems most convincing to me must be true.”
That would be an appeal to intuition.
It also doesn't mean:
“If I can't think of a better explanation, my explanation is proven.”
That would be an argument from ignorance.
Instead, the proper conclusion is usually something like:
“Given the evidence currently available, hypothesis A provides a better explanation than hypotheses B and C.”
And if new evidence appears, the conclusion can change.
This type of reasoning is particularly important when we cannot directly observe the event we're trying to explain.
For example, historians might ask:
“What best explains the evidence we have concerning an ancient event?”
They compare:
contemporary documents,
later accounts,
archaeological evidence,
independent sources,
eyewitness testimony,
known historical background,
and competing explanations.
This is also why IBE is frequently used in science, history, archaeology, forensic investigation, and philosophy.
A useful way to remember it is:
Deduction:
What must be true?
Induction:
What is probably true based on a pattern of observations?
Inference to the best explanation:
What hypothesis best explains what we observe?
And importantly, IBE can be extremely strong without producing deductive certainty. That distinction becomes especially important in philosophical and historical arguments.