I’ve written in the past about instrumentalism, the scientific practice of treating theories as tools that can be evaluated by their usefulness, rather than as claims that can be evaluated as true or false. If you haven’t tried this way of looking at science, I highly recommend it! But if theories are tools, what are they used for? What makes a theory more or less useful?
The process of science starts when someone makes an observation about the world. If we don’t understand the observation, we need to explore more, make more observations. We make hypotheses and test them, trying to get to a general principle that we can apply to a whole range of situations. We may then look for ways to apply this principle to our interactions with the world.
At every step of this process there is communication. The person who makes the initial observation, the people who make the further observations, who make the hypotheses, who test them, who who generalize the findings, who apply them: these are usually multiple people. They need to communicate all these things (observations, hypotheses, applications) to each other. Even if it’s one single person who does it all end to end, that person needs to communicate with their past and future selves, in the form of notes or even just thinking aloud.
These observations, hypotheses and applications are always new, because that’s what science is for: processing new information. It’s hard to deal with new information, to integrate it with the systems we already have for dealing with the world. What helps us in this regard are finding similarities between the new information and things we already know about the world. Once we find those similarities, we need to record this for our own reference and to signal it to others: other researchers, technologists and the rest of the population.
In informal settings, we already have ways of finding and communicating similarities between different observations. We use similes and metaphors: a person’s eyes may be blue like the sky, not blue like police lights. These are not just idle observations, though: the similarities often have implications for how we respond to things. If someone is leaving a job and they say that they’re passing the baton to a new person, they are signaling a similarity between their job and a relay race, and the suggestion is that the new person will be expected to continue towards the same goal the way a relay runner continues along the racecourse.
Theories and models are just formalized versions of metaphors: saying that light is a wave is a way of noting that it can move through the air like a wave moves through water. That theory allowed scientists to predict that light would diffract around objects the way that water waves behave when they encounter objects, a testable hypothesis that has been confirmed. This in turn allowed technologists to design lasers and other devices that took advantage of those wavelike properties, applications that have proven useful.
Here’s a metaphor that will hopefully help you understand how theories are communication tools: another communication tool is a photograph. Sometimes I see a photograph of myself and I notice that I’ve recently lost weight. Let’s say that I have been cutting back on snacks and I see a photo like that. I have other tools for discovering that I’ve lost weight, like scales and measuring tape and what I can observe of my body with my own eyes, but seeing a photo can communicate it to me in a different way and suggest that if I continue cutting back on snacks I will continue to lose weight. Similarly, if I post that photo on Facebook my friends can see that I’ve lost weight and understand that I’m going to continue to cut back on snacks.
A theory is like a photograph in that there is no single best photograph. To communicate my weight loss I would want a photo that shows my full body, but to communicate my feelings about it, a close-up on my face might be more appropriate. Friends of mine who get new tattoos on their legs will take close-ups of the tattoos. We may have six different photos of the exact same thing (full body, face or leg, for example), and be satisfied with them all. Theories are similar: they depend entirely on the purpose of communication.
A theory is like a photograph in that the best level of detail depends on what is being communicated and who the target is. If a friend takes a close-up of four square inches of their calf, that may be enough to show off their new tattoo, but a close-up of four square inches of my calf will probably not tell me or anyone else how much weight I’ve lost. Similarly, if I get someone to take an aerial photograph of me, that may indicate where I am at the time, but it will not communicate much about my weight. This applies to theories: a model with too much detail will simply swamp the researchers, and one with too little will not convey anything coherent about the topic.
A theory is like a photograph in that its effectiveness depends on who is on the other end of the communication. If someone who doesn’t know me sees that picture, they will have no idea how much I weighed before, or that my weight has been affecting my health. They will just see a person, and interpret it in whatever way they can.
A photograph may not be the best way to communicate my weight loss to my doctor. Their methods depend on measurable benchmarks, and they would prefer to see actual measurements made with scales or tape. On the other hand, a photo is a better way to communicate my weight loss to my Facebook friends than posting scale and tape measurements on Facebook, because they (or some of them at least) are more concerned with the overall way I look.
A theory’s effectiveness similarly depends on its audience. Population researchers may be familiar with the theories of Alfred Lotka and Vito Volterra, so if I tell them that ne…pas in French follows a Lotka-Volterra model, they are likely to understand. Chemists have probably never heard of Lotka or Volterra, so if I tell them the same thing I’m likely to get a blank stare.
This means that there is no absolute standard for comparing theories. We are never going to find the best theory. We may be able to compare theories for a particular purpose, with a particular level of detail, aimed at a particular audience, but even then there may be several theories that work about as well.
When I tell people about this instrumental approach to scientific theories and models, some of them get anxious. If there’s no way for theories to be true or false, how can we ever have a complete picture of the universe? The answer is that we can’t. Kurt Gödel showed decades ago with his Incompleteness Theorem that no theory or model can ever completely capture reality, not even a mathematical or computer model. Jorge Luis Borges illustrated it with his story of the map that is the same size as the territory.
Science is not about finding out everything. It’s not about getting a complete picture. That’s because reality is too big and complex for our understanding, or for the formal systems that our computers are based on. It’s just about figuring out more than we knew before. It will never be finished. And that’s okay.