| | Michael Smith wrote, "An absence cannot be cited as evidence of a presence. A lack of information cannot be cited as information about something else. An absence of facts cannot be interpreted as proof of the existence of anything."
I agree with this. But I'd like to raise a point that is sometimes overlooked in discussions of this sort. Suppose the prosecution presents evidence sufficient to warrant a conclusion that the accused is guilty, and the defense presents no counter-evidence - no challenge to the prosecution's case. In that event, we are justified in concluding that the accused is guilty, because there is no reason to doubt the evidence presented by the prosecution.
But suppose the defense does present counter-evidence - does present material that challenges the prosecution's case and thus creates a reasonable doubt as to the defendant's guilt. In that case, we are no longer justified in concluding that the defendant is guilty beyond a reasonable doubt.
In the first case, we are justified in concluding that the defendant is guilty, because of the absence of any evidence that he is innocent. All the evidence supports his conviction and none contradicts it. In the second case, we are no longer justified in concluding that the defendant is guilty, because of the presence of information that challenges the evidence presented by the prosecution.
To be sure, the absence of evidence presented by the defense is not evidence for the prosecution; the prosecution must have independent evidence that the accused is guilty. But the absence of evidence against the prosecution's case can make a difference in whether or not it is reasonable to conclude that the defendant is innocent or guilty.
A short while ago, when I was participating on Diana Hsieh's blog, an issue arose concerning a notorious essay by Chris Wolf entitled "My Dinner with Andy," in which the author criticized Andrew Bernstein's conduct as rude and boorish during a dinner party to which Wolf had invited him. Wolf's comments were dismissed out of hand by the other participants on the blog as unworthy of serious consideration, because they did not fit the positive impression that the posters there had of Mr. Bernstein. I said that I saw no reason to doubt Wolf's comments, since it is extremely unlikely that he would publicize them on his blog, if they were an obvious fabrication. After all, I said, there were many other people at the dinner who could easily have exposed his remarks as false and malicious. And since none had done so, I argued that there were no grounds on which to dismiss his story. I noted that the incident occurred many years ago, and that it was reasonable to think that Mr. Bernstein's conduct could well have improved since then. Or it may have been that he simply had a bad day and that his rude conduct was uncharacteristic. But I didn't see how we were justified in concluding that Wolf's essay was a deliberate fabrication without any evidence from the other dinner guests disputing his story.
Unfortunately, my comments were not well received and I was told by the moderator, Ms. Hsieh, that any further comments I made on this subject would be deleted from her blog. She then accused me of violating the onus of proof principle - of demanding proof of a negative - because I had said that I was willing to accept Wolf's comments at face value in the absence of contradictory statements from others who had witnessed the event. She argued that the mere fact that others had not contradicted him did not prove that what he said was true - that the absence of evidence against something is not evidence for it - because the other dinner guests could simply have had no interest in challenging his remarks (very unlikely, if the remarks were clearly false), or they may not have been aware of the essay that he posted (also very unlikely!). She then argued that based on comments Wolf had made in other contexts, he was not to be believed, because the man is, to quote her, "a raving lunatic." One wonders if she had evidence sufficient to support that allegation.
Of course, the important point here, and the one that I was defending, is not that the absence of evidence against something is evidence for it, but that the absence of evidence against something could very well mean that the evidence for it is sufficient to conclude that it's true.
- Bill
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