What counts as "evidence"?

This post is a response to a question posed by Vincent Torley, "Is Larry Moran a conspiracy theorist?"

A few weeks ago the Toronto Star (Toronto, Ontario, Canada) published a front page article on the dangers of Gardasil, a vaccine against human papillomavirus (HPV) that's recommended for adolescent girls. The article highlighted a number of anecdotal stories about girls who had developed various illnesses and disabilities that they attributed to the vaccine. The reporters thought this was evidence that the vaccine had serious side effects that were being covered up by the pharmaceutical industry.

Almost every scientist who read the story recognized that correlation does not mean causation and that the "evidence" promoted by David Bruser and Jesse McLean was no different than the claims of Jenny McCarthy and her supporters about the MMR vaccine and autism. There were dozens of health professionals and scientists who criticized the article in the Toronto Star culminating in a op-ed article that clearly pointed out all the flaws in the original piece [Science shows HPV vaccine has no dark side]. That article was signed by 63 scientists and physicians.

The newspaper's public editor (ombusdman) concluded that the story was misleading [Public editor criticizes the Star's Gardasil story] and two weeks after the article was published it was taken off the Toronto Star website [A note from the publisher].

It's not hard to see where David Bruser and Jesse McLean went wrong. They assumed that anecdotal evidence, or personal testimony, was evidence that Gardasil had serious side effects. They assumed this in spite of the fact that scientists and philosophers have been warning against this form of reasoning for 100 years. They assumed it in spite of the fact that there was abundant scientific evidence showing that Gardasil was safe. And they assumed it without bothering to investigate the stories. (see what David Gorski of Science-Based Medicine found in just a few minutes of searching the internet [How not to report about vaccine safety issues, Toronto Star edition].)

David Bruser and Jesse McLean were wrong. There is no evidence to support their claim.

Now, it's possible that accumulating stories like those will eventually lead to further investigation and the discovery that there are, indeed, some rare side-effects that went undetected in the initial studies. When that happens, we will have evidence. But as long as there are better explanations for those stories they are not evidence of a serious problem with the vaccine.

The issue is what counts as "evidence" and how do we recognize it?

A while ago I responded to Vincent Torley's post of the evidence for god(s) [Vincent Torley and the evidence for god(s)]. I claim that there's no evidence of god(s) but I qualified it by saying,

When I say there's no evidence for the existence of god(s) I mean that there is no "evidence" that stands up to close scrutiny. That's not quite the same thing as saying that there's no "evidence" that others might believe or no potential facts that are presented as possible evidence.

It's an important distinction to keep in mind but It think it quite clear that when I say there's no evidence for the existence of god(s) I mean that there's no valid evidence. That brings up the question of what defines "valid evidence." The short answer is "I don't know" but I know it when I see it.

This was my attempt at being as honest and forthright as possible. I don't know how to define "valid evidence" and I doubt very much if there's anyone else who can offer a rigorous definition.

To a creationist this is as much as admitting that I was wrong. But it's worth noting that they haven't supplied a definition either.

I picked one example from Vincent Torley's list.

Torley says that there's evidence of miracle and this is evidence of god(s). His "evidence" consists of reports by eighteenth century theologians that thousands of people witnessed St. Joseph of Cupertino flying through the air.

I reject the notion that this constitutes evidence that St. Cupertino could actually fly. There are far better explanations for the reported observations; namely, that they aren't true. One of the characteristics of valid evidence has to be whether the purported explanation is a logical conclusion from the observation. In this case, is it more reasonable to assume that thousands of people saw St. Cupertio fly or is it more reasonable to assume that they all just imagined it, or that the second-hand reports are untrue?

If thousands of people reported that St. Cupertino just walked around in the garden then that would be quite unremarkable and we could tentatively accept it as true even if we remained skeptical about eyewitness reports. But when you make an extraordinary claim that goes against all experience, then the evidence has to be truly extraordinary in order to even qualify as evidence.

I don't believe that St. Cupertino actually flew around parts of Italy in the 1600s because there are much more reasonable explanations for the reports that have been written. Those naturalistic explanations don't require all the extra baggage that you have to take on if you assume that the reputed observations were true. (For example, is it only Roman Catholic priests that can fly and why haven't there been any sightings in modern times?)

Vincent Torley's example is not evidence that something extraordinary happened and it certainly isn't evidence that god(s) exist.

What was his response? He repeated the claim that flying priests were a FACT that proved the existence of miracles.

But the most ridiculous part of professor Moran’s reply relates to the occurrence of miracles. In my post, I focused on one particularly well-attested miracle: the levitations of the St. Joseph of Cupertino, who was seen levitating well above the ground and even flying for some distance through the air, on literally thousands of occasions, by believers and skeptics alike, in the seventeenth century. I referred curious readers to a biography by D. Bernini (Vita Del Giuseppe da Copertino, 1752, Roma: Ludovico Tinassi and Girolamo Mainardi), as well as an online article, The flying saint (The Messenger of Saint Anthony, January 2003), by Renzo Allegri.

I stand by my opinion that there is a better explanation for Vincent Torley's claim.

Here's comes the attempt to be scientific ....

Professor Moran cites Sagan’s dictum that extraordinary claims require extraordinary evidence. But he never attempts to give a quantitative answer to the question: “How extraordinary must the evidence be?” The evidence for naturalism is, at best, cumulative. Given that the number of discrete events (or elementary bit-operations) that have occurred during the history of the universe has been estimated at less than 10^150, it follows (using Laplace’s famous sunrise argument) that the probability we should assign to the claim that the next event we witness will not be a natural one can be no lower than 1 in 10^~120. Hence if we can calculate that the combined probability of thousands of eyewitnesses hallucinating and/or perjuring themselves about having witnessed a levitation when they didn’t – and remember, back in those days, everyone in Italy really believed that perjury was a sin you could go to Hell for committing – on thousands of occasions is less than 1 in 10^~120, then the hallucination and fraud hypotheses become even more extraordinary than the hypothesis of a miracle, which then becomes the most rational one to adopt. Since the sightings occurred on multiple occasions and a multiple locations, we can treat them as independent events, and calculate accordingly. Thus it is not difficult to obtain a figure far lower than 1 in 10^~120. Take that, Carl Sagan! [my emphasis]

It's clear that Vicent Torley and I have different views on what constitutes evidence but also far different views on the meaning of the word "rational."

Torley raises two other points in his latest post. The first one concerns the origin of life ...

I was hoping that Professor Moran would provide a detailed critique Dr. Koonin’s calculations in his latest reply, but none was forthcoming. On the basis of these calculations, coupled with the multiple failings of the multiverse hypothesis, I can only conclude that the origin of life points to its having had a Designer of some sort – a point which Professor Moran still refuses to acknowledge. To his credit, however, he has recently conceded that “We don’t know how the first information-containing molecules arose and how they came to be self-replicating,” and has also declared himself to be skeptical of the “primordial soup” and “RNA world” hypotheses.

Eugene Koonin's calculations are silly. I have no idea how to discuss them.

I don't know how life originated. That statement gets me in trouble with many defenders of evolution because they think it concedes too much to the creationists. Frankly, I don't care. It's the truth and we need to be up front about it. Just because we don't know doesn't mean that a naturalistic origin of life is impossible. On the contrary, everything we do know is consistent with a spontaneous, natural, origin of life. It looks to me like it was a very rare event but it's a big universe.

What about the idea that god(s) did it? As Pierre-Simon Laplace is reported to have said to Napoleon, "I have no need of that hypothesis."

Life on Earth began about 3.5 billion years ago. It is not evidence of god(s).

Torley's second objection concerns the fine-tuning argument. Creationists like to think that this is evidence of god(s) but it's not. Here's what Vincent Torley says,

After this poor start, Professor Moran’s attack on the fine-tuning argument continues to go downhill. Moran’s comments reveal that he has completely failed to grasp the logic of the fine-tuning argument. He flippantly dismisses the argument on the grounds that “[w]e could not possibly find ourselves in any universe that was not compatible with the existence of life.” But this remark is utterly beside the point. For proponents of the fine-tuning argument do not argue that because we happen to live in a life-friendly universe, therefore it must be designed. Rather, what they argue is that because we live in a universe which would be incapable of supporting life if its fundamental parameters were even slightly different, it is reasonable to infer that our universe is a put-up job.

No, it is not reasonable to assume that god(s) exist.

The universe may not be as "fine-tuned" as most creationist believe. Anyone who has read Victor Stenger will know that it's not an open-and-shut case [Fine-tuned Universe]. Let's assume for the sake of argument that the universe is "moderately-tuned for life as we know it." We don't know how many other kinds of universe are possible and we don't know how many different kinds of life are possible. All we know is that we are here and, not coincidentally, the existing universe is compatible with our presence.

If the present universe arose by completely random naturalistic events then we would still be here discussing it. To leap from there to the claim that supernatural beings must exist is neither reasonable nor logical. The entire fine-tuning argument is based on the assumption that multiple universes are possible and the one we find ourselves inhabiting was picked from an infinite array of possibilities by some committee of supernatural beings that existed outside that universe some 13.8 billion years ago.

I have no need of that assumption and the existence of this universe is not evidence that the assumption is correct. It's basically an argument from ignorance and in this case "ignorance" (i.e. not knowing) is the only logical conclusion. We don't know for sure why the universe has the properties it has.¹ I hope we'll know more in the future but even if we don't, that's no reason to convert to Christianity.

It seems to be extraordinarily difficult for believers to grasp the essence of the "puddle argument" described by Douglas Adams. I suspect that's because they already believe that their god(s) exist and that he/she/it/they created the universe. The fine-tuning argument then becomes justification for their beliefs. They mistakenly think that it is extraordinary "evidence" for their god(s) and they just can't cope with the fact that hundreds of millions of atheists don't agree with them.

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1. Yes, I know that we aren't completely ignorant. I'm addressing the logic of the argument not the evidence for a moderately-tuned universe.