The Advantages and Disadvantages of Including Purpose

Across the natural sciences and history, there are advantages and disadvantages of thinking with a purpose-based mindset.

The biggest shortfall of thinking in this way is that if you believe you know how the story ends, you may tell it in a way that ignores everything that does not lead to that ending. And that will leave out many other things, including actors or stories that might turn out to be essential. In other words, even if there really is an ultimate purpose to something, you may misidentify that purpose and miss important aspects of the story. Partly for this reason, historians are wary of teleological histories written as though the purpose of the past was to get to “us”—whether “us” means modern global society with capitalism and democracy and computer technology, or whatever one’s favorite aspect of the present is. This is problematic insofar as it makes the present-day world seem inevitable, funneling everything into a single narrative and failing to properly account for contingency. As mentioned earlier in this chapter, the historian Herbert Butterfield famously pointed out that this combination of progress, purpose, and presentism makes for sloppy thinking about the past.

An analogous example from the realm of natural science, rather than human history, comes from the study of the nucleic acid RNA [...] and the roles it plays in the cell. For many years after its discovery, RNA was thought to serve as an intermediary in “translating” DNA blueprints into protein molecules. This is certainly a major role that RNA plays, but a considerable amount of RNA in cells does not participate in translation. In part because they thought ofRNA as having just one particular purpose, biologists considered that this other RNA had no function in the cell—and even labeled it “junk RNA.” But it turns out that this supposed “junk” actually performs a variety of functions that at the time were unknown. Arguably, identifying the purpose of RNA too narrowly led cell biologists to miss significant parts of the overall picture of RNA’s importance to the cell.

Similarly, in the evolutionary history of life, simple teleological progress narratives are problematic [...] Questions like “Why did humans become bipedal?” or “Why did brains develop?” are usually answered with proximate explanations, not with grand, overriding purposes. Populations of organisms adapt to their surroundings, but they do not evolve toward some overall common goal identifiable to biology.

On the other hand, there are also many good reasons why teleological language and reasoning about purpose persist in both the sciences and history. In human history, after all, humans certainly think they pursue purposes—intentionally!—both individually and collectively. And the biological world also presents many situations where thinking in terms of purpose is so helpful for understanding organisms that it is difficult to make sense of life, at any scale, entirely without it. Using ideas of purpose to understand life can lead scientists to discover things they might not have identified otherwise. The RNA example, for instance, shows that assuming the absence of purpose just because science has not yet identified something as being purposeful does not mean that it really is purposeless.

In evolutionary biology, where ideas about purpose may be most fraught, there are still good reasons to explicitly consider purpose. One reason is that the overarching Darwinian framework of natural selection leaves the ultimate origin of any teleological character of organisms largely unexplained. Most notably, it invokes survival and reproduction as given realities of life, but survival (self-maintenance) and reproduction are themselves purposes that organisms—all organisms—pursue. This is foundational, definitional, in the very category of “life.” It is not that individual organisms “want” to evolve. But consciously or unconsciously, individual organisms do pursue purposes in surviving and reproducing, purposes that are basic to life at every level: cellular, organismal, species, and ecosystem. According to a founding figure in evolutionary biology, Theodosius Dobzhansky, “Living beings have an internal, or natural, teleology.” There is therefore a key sort of intrinsic goal-directedness. Or as J. B. S. Haldane, another founder of the modern evolutionary synthesis, quipped, “Teleology is like a mistress to a biologist: he cannot live without her but he’s unwilling to be seen with her in public.”

The value of purpose-based thinking may extend to the physical sciences as well, although it can be harder to see. Ruse comments, “Nobody expects atoms and molecules to have purposes,” and yet one could argue that atoms, the building blocks of matter, are perfectly ordered to be precisely that: the building blocks of matter. They are stable because the charge on the electron matches the charge on the proton, among many other properties; this basic fact is not something that any current fundamental theory of physics explains, but rather takes as a given. The structure of an atomic nucleus, including both protons and neutrons, allows the formation of different elements. The ability of a nucleus to undergo fission and fusion has allowed the creation of all manner of new elements in stars. It is completely consistent with everything we know about atoms to say that their purpose is to be the stable, fundamental building block of ordinary matter. Final cause can, in this way, throw light on why the atom is the way it is.

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Cameron Gibelyou and Douglas Northrop, Big Ideas: A Guide to the History of Everything (New York: Oxford University Press, 2021), 316-319 (footnotes omitted).