One night this month, Keith was out at an evening meeting, so I threw food on the dinner table, mac and cheese, olives (my kids love olives), grapes–stuff that’s fast and with a low complaint-to-acceptance ratio. I sat down to eat with them, while recordings of my conversation with an Italian jellyfish scientist named Fernando Boero reverberated in my head. I’d been wrestling with his philosophy all week.
I put a conjecture to my kids, as Boero did to me. ”Suppose I tell you that all jellyfish are clear. Then you go to the beach and find 50 clear jellyfish. Can you say that my statement is true?”
“No,” Isy says, surprising me a little because she usually has little tolerance for my brain games. I guess she was in a forgiving mood tonight. “You haven’t looked at all the jellyfish in the world.”
“Right. You can’t prove all the jellyfish are clear because you can’t look at all the jellyfish in the world. How about this, could you prove that all jellyfish are not clear?”
Ben, not to be outdone by his little sister, chimed in. “Yes, you could find a white or blue or other colored jellyfish.”
This idea–that testable theories can only be negated–was first put forward by a naturalist named Karl Popper, and so became known as Popperian logic. It’s a line of reasoning that some people used to argue about the existence of God. You can never prove a positive, so you can never prove God exists. Popper goes well beyond my understanding, but I’m trying to get a handle on this small bit.
“OK.” I ask, “What about this statement: There’s a purple jellyfish in the bay. Can you prove that true?”
Isy gets this one. “Yes, you could prove that if you look in the bay and you see a purple jellyfish.”
“Right. Can you prove it false? Can you prove that there is no purple jellyfish in the bay?”
“No, you can’t look everywhere in the bay at the same time. You can’t prove that there’s not a purple jellyfish hiding somewhere that you aren’t looking.” That’s Ben, still engaged – though I’m getting close to losing him if I don’t make my point soon. Isy, eating macaroni noodles with her fingers, one-by-one, has already faded from the conversation.
I turn to Ben. “What’s the difference between the two statements? What makes it impossible to prove that all jellyfish are clear, but possible to prove that there’s a purple jellyfish in the bay?”
Ben is on it. “The first statement can be for anywhere. But the second one is for the bay only.”
The point of all this is to understand that statements about the universe can’t be proven, but a statement about a specific domain, also called an existential statement, can. I had to think about this idea for a while after Boero first told me about it. I wasn’t sure I understood until I went back and listened again to our conversation, and then forced it on my kids over dinner.
The reason I really wanted to understand the difference between universal and existential statements it is because Nando has a theory that this difference helps explain why the public mistrusts scientists, and that’s something I’ve been thinking about a lot. Actually, Nando doesn’t think the public mistrusts all scientists. He thinks the public specifically mistrusts biologists.
Physicists can make universal statements: The universe is expanding. All objects are attracted to each other according to their mass and the distance between them. All stars eventually explode, and so will our Sun one day. These statements are universal. That’s satisfying. There’s comfort in definite answers, even if they predict the end of our solar system.
On the other hand, biological statements tend to be about particular domains. They have clauses and exceptions. They say what exists in the particular place or at a particular time or under particular conditions: the purple jellyfish in the bay. Biology can tell you that in the Mediterranean the mauve stinger used to cycle on roughly 12 year intervals, but lately that frequency has shot up; in the Arctic jellyfish numbers increased for several years, but then fell; big bloom years for giant jellyfish in Japan used to happen once a generation, until this century. It’s very difficult–maybe impossible–for biologists to make the universal statement: jellyfish populations are exploding. Each species on this planet exists because of a unique set of evolutionary pressures that molded it into what it is today. No two species have the same story.
Biologists often get stuck in the morass of trying to make universal statements where there are none to make. Universal statements are big and bright, and headline grabbing: “Jellyfish are taking over the oceans.” But the reality is that biology is so complicated those universal statements don’t work. Some jellyfish are on the rise in some places for different reasons. Sometimes it’s acidification. Sometimes its coastal development. Other places it’s overfishing. Or warming. Or often a combination. Each time we find out it’s one or the other or several, we prove the remaining theories wrong.
This mismatch between universal and existential statements might be the root of much misinterpretation by the media and policy-makers. And that’s annoying, or worse. It pisses people off and provides fodder for denial.
In 2009 I followed along during the controversy over state science standards in Texas. At the time I was writing science textbooks, and the standards were the scaffolding I used daily to develop educational material. At issue was the wording of a science standard that stated students must be taught the “strengths and weaknesses” of evolution. Scientists view these three words as a means for inserting the creationist theology that goes under the name intelligent design into science classes.
After weeks of following the proposed changes to the standards online, and then more weeks of sitting in the back of the hearing room fuming at the I scientific ignorance of the elected officials on the state board of education who get make these decisions, I decided to say something.
As I walked to the podium in the hearing room, I looked out at 15 Board members seated in an oval, the state seal of Texas emblazoned into the leather chair backs just above their heads. Seven members were staunch supporters of “strengths and weaknesses”. I was speaking to the one swing vote.
“Thank you to the Board of Education for taking my testimony,” I began. “For the last decade I have worked in the textbook publishing industry: writing, editing and developing curricula for science textbooks. While I am certain of my expertise writing scientific text, I don’t want, nor should you want me to have, the responsibility for writing textbooks containing information that is not scientific fact.”
I concluded. “I urge you to uphold language that supports the rigorous teaching of evolution to our students. I wouldn’t want students to read fiction in a history book and try to determine which part of their text is historical fact. Why would you want students to read non-scientific ideas in a science book?”
Questions followed. “If the language ‘strengths and weaknesses’ were included in the standard, would you feel the need to include weaknesses of evolution in your text?”
My voice was tight and reedy. “It’s really hard to come up with scientifically based weaknesses to evolution.” The intelligent-design supporters exploded in protest.
The chairman banged his gavel repeatedly. “I will not have that kind of outburst in this room. If it happens again, I’ll clear the room and we’ll only have the testifiers in here. I’ll do it!”
When the votes were tallied, the language “strengths and weaknesses” didn’t make it into the standards, but other language was inserted that questioned the big bang and the cell as the basic unit of life. As one observer pushing for scientifically-sound standards said, “We shut the door on “strengths and weaknesses”, but they threw open all the windows.”
After it was over, I was left wondering whether adding my voice to the fray had any impact on the outcome. The battle felt bigger than just the words “strengths and weaknesses” and I still believe it is. And Boero’s distinction gave me some new insight into the problem.
Creationists point to a number of observations evolution can’t explain better than the idea of a directed designer: the complexity of the eye and the flagella and the massive explosion of species in the Cambrian are among the most commonly cited. Biologists recognize such problems are not well understood, but expect to solve them given enough time to study the specifics of each problem. Those solutions will be existential. Figuring out how a flagella evolved probably won’t have anything to do with how an eye evolved. Each will be a purple jellyfish in a bay.
But the creationists want more than that. They want universal solutions, solutions that apply in all cases at all times. Finding one purple jellyfish isn’t enough. They want a statement that incorporates all the jellyfish. The theory of an intelligent designer directing the diversity and complexity we see around us has that universality. Biological answers will never satisfy a creationist because the two sides are working in entirely different philosophical spaces.
But here’s where I get hung up. If the theory of an intelligent designer is universal, it can’t be proven true, as my kids pointed out with the example of all jellyfish being clear. However, it should be able to be proven false if you find one exception. And biologists have found examples of evolution by the journal-flu and by the textbook-ful.
This is not a problem that is not going to be solved anytime soon. The battle will rage on. But when the next opportunity comes to bring it up at dinner with my kids, we’ll be talking it over.