Wednesday, December 05, 2007
Inference
I woke up this morning to see snow on the ground where there was none before. I slept soundly through the night, and I did not awaken at any point. I did not see snow falling during the night. Yet it is reasonably to infer that indeed it snowed during the night; it would be absurd to deny it.
This is a good demonstration of the power of inference. We infer all day, every day. We could not function if we required, in ordinary decision-making, direct evidence of each fact we considered.
There is nothing wrong with an inference per se. It may be less persuasive than direct evidence -- for example, awakening in the night, looking out the window, and seeing the snowflakes coming down -- but it can be only slightly less persuasive. The inference should be evaluated on its strength -- i.e., how many times has direct evidence proven the same proposition, reliably -- and not dismissed merely because it is an inference. The argument against an inference should be framed as "That inference is unwarranted, because . . ." and not as "That is an inference, and therefore unwarranted."
