The Absence of Elephants
You’re sitting at home on a Sunday afternoon, watching golf on television, which is to say that you are half-asleep, when the phone rings. The caller is one of your neighbors, and he says that there is an elephant in your front yard. You go to the window, you look out on the front yard, and there is no elephant there. You go back to the phone and say to your neighbor, “Good one. You made me look.” Then you hang up and go back to your golf.
I can divide your knowledge about elephants in your front yard into three states. In the first place, before the phone rings, you have no information. There is an absence of any evidence, as far as you know, regarding the presence or absence of elephants in your front yard. In fact, the possibility hasn’t even been raised. (It may be a general rule that a genuine absence of evidence coincides with a lack of interest in the question at hand.)
In the second state, after your neighbor calls, you have one piece of evidence: your neighbor’s testimony that an elephant is in your front yard. This may or may not seem likely to you, depending upon where you live and your prior experience. Under the principle of induction, if there has never been an elephant in your front yard before, it may seem unlikely that there is one at this time. However, the inductive problem, which indicates that any inductive conclusion can be overthrown by a single contrary example, implies that one should always be aware of the possibility of an instance contrary to one’s prior experience. One might call this keeping an “open mind.” Therefore, you go to the trouble of looking at the front yard, rather than dismissing your neighbor’s statement as a lame joke.
Finally, after you have looked at the front yard, you have another piece of evidence: your visual inspection of the yard shows that there are no elephants there. This evidence contradicts your neighbor’s statement, and (in your opinion) is conclusive. If you don’t see an elephant, there isn’t one. Your conclusion is that there is no elephant in your front yard.What I want to make clear with this example is that the absence of an elephant is not an absence of evidence concerning elephants. You have evidence concerning elephants, and this evidence is negative. That is, you have evidence of the absence of elephants. More generally, the absence of a phenomenon is not the same as the absence of evidence relevant to the existence of that phenomenon. Negative evidence is not the same as the absence of evidence.
The Case of Iraq’s Weapon’s Programs
Where Mr. Rumsfeld went wrong was in identifying an absence of material showing a particular outcome with an absence of evidence about that outcome. In fact, due to United Nations’ inspections, U.S. intelligence, and Iraqi reports, there was a lot of evidence about weapons of mass destruction in Iraq. On the one side, you had statements from Saddam Hussein and some of his underlings affirming that some weapons programs were in operation. (Whether they believed their own statements, or were running a bluff, is still uncertain.) On the other side, you had on-site inspections of places where such activities had taken place in the past, as well as places identified as suspicious by intelligence agencies, all of which showed that Iraq had complied with orders to terminate these programs.
In other words, the “elephant” in this case were weapons of mass destruction (WMD), and programs to manufacture and distribute them. Saddam Hussein himself, and certain intelligence sources claimed that there were active WMD in Iraq. On-site inspection, documentation, and a variety of intelligence sources contradicted those claims. Some photographic intelligence, much of which was (and always is) inherently ambiguous, supported the affirmative case. Other evidence supported the negative.
However you might wish to characterize the situation in Iraq in 2002 and 2003, an absence of evidence was not the problem. The problem was that the evidence available did not all point in one direction. It was not dispositive. It was clear that some of the weapons programs that had been in operation prior to 1991 were no longer functioning, at least not at the same scale or in the same places as they had been. It was clear that a lot of material had been destroyed under the sanctions regime, while there were no findings to show that it had been replaced. It also appeared that Saddam Hussein had the intention, or at least the wish, to develop WMD, if he ever had a free hand to do so.
In the end, by deciding to justify the invasion of Iraq on the existence of WMD, the Bush administration asserted that the affirmative evidence was more compelling than the negative evidence. A lot of people think they were wrong. To the extent that they dismissed the negative evidence as “an absence of evidence,” they were certainly wrong.
The absence of evidence means that one has no information about a subject. The absence of proof that something exists is not the same thing as the absence of evidence regarding its existence. Once one has evidence, one must evaluate it. Often, one needs to seek additional information to determine whether the initial evidence is credible or not. In many cases, the evidence is ambiguous or contradictory. Frequently, as in Iraq, the problem is not an absence of evidence: it is an inability rightly to assess the evidence one has.