When we notice an interesting feature of a living organism we often ask, “What is it for?”. What are the showy stripes of a zebra for? What about the sticky latex secreted by milkweed leaves when cut, what's that for? We might ask the same question about a feature of an artifact created by humans, past or present, or even the whole artifact. What is the rounded head of a ballpeen hammer for? What about the elaborately arranged collection of boulders at Stonehenge? But we don’t usually ask this question about inanimate natural objects, like boulders found in natural settings, or wind, or water.
This post will situate this question in the broader way of thinking about functions that scientists sometimes find themselves doing. The goal is to present a stepping stone between the profound question about function, and the theories that have been presented as solutions.
Photo credit: Kimber Nilsson via Unsplash
To ask what something is for in this way is to ask about its function, to assume that it has a function, and inquire what the function is. But what is a function? What kinds of things really have functions? These questions turn out to be surprisingly difficult to answer. They become even more challenging when we notice that “function” here might be another word for “purpose.”
It seems easy to understand purposes in artifacts. The purpose of a piece of technology is whatever its designer intended it to do. At least, that’s an obvious possibility, though there are others. But let’s go with that one for now. But what about natural things? Are there natural purposes, purposes that don’t depend on what someone had in mind?
Many scientists and philosophers have answered that question with a sharp “No.” In fact, a great deal of scientific effort has been spent in trying to get rid of notions of purpose (teleological notions) in the natural sciences. There are many reasons for this, and we’ll look at a couple of important reasons in a minute. But in a way, all the reasons are versions of a single underlying idea: that “purpose” is a metaphysical idea, not something that can be observed. Therefore, science can’t say anything about it, and it has no place in a scientific worldview. Yet many scientists, especially those dealing with living things, talk about functions all the time. Is there a way of thinking of purposes, or at least functions, that
is compatible with scientific principles?
This blog will come to cover several theories, namely, the selected-effects, the causal-role view, the organizational view, and the persistence view.