⁂ Concepts · Cause · No. 32
Teleology

Four and a half metres for a journey of a few centimetres, and it still works.

Teleology

Explanation by what something is for - expelled from physics, indispensable in biology, and still unsettled.

Theme
Cause, time and change
Tradition
Cross-tradition
Term
τέλος · telos
Term fixed
c. 330 BC

In plain terms

The heart is for pumping blood. That sentence is true, everyone understands it, and it is doing something no purely causal description does - it says what the heart is for.

Physics abandoned this kind of explanation in the seventeenth century, and the abandonment was an enormous success. Stones do not fall in order to reach their natural place; they fall because of forces, and looking for purposes in mechanics was holding the subject back.

Biology never managed to do without it. No biologist can describe an eye, an enzyme or a defence mechanism without saying what it does and what it is for, and attempts to purge the vocabulary have produced circumlocutions rather than replacements.

Which leaves the question of what those statements are claiming, given that nobody designed any of it.

As a philosopher would put it

Aristotle's telos is a genuine explanatory principle rather than a claim about intentions: an acorn's development toward an oak is explained by what it is developing into, and no designer is required.

The mechanist revolution expelled final causes from physics on the ground that they explain nothing and impede inquiry - Bacon's remark that the final cause is like a virgin consecrated to God and barren is the standard citation.

Biology's persistence produced the modern accounts. Etiological theories, principally Wright's and Millikan's, define a function as the effect for which a trait was selected: the heart is for pumping because pumping is why hearts were selected. That grounds purpose talk in history and makes function claims genuinely true or false. Causal-role theories, following Cummins, define function by contribution to a containing system's capacity, which handles current organisation and cannot distinguish a function from an accident.

Kant's formulation anticipates the difficulty: organisms must be judged as if purposive, and the as-if is doing real work.

Where you meet it

The recurrent laryngeal nerve connects the brain to the larynx. In every tetrapod it does not go directly. It descends into the chest, loops under an artery near the heart, and returns up the neck.

In a human that detour is a few centimetres. In a giraffe it is around four and a half metres for a journey of a few centimetres, and the arrangement is present in sauropods, where it would have run tens of metres.

The explanation is developmental history. In fish the nerve runs straight past the relevant arch; as the neck elongated over evolutionary time, the nerve was dragged along, and no step of that process could have detached and rerouted it.

The nerve has a function - it innervates the larynx, and damaging it costs the voice. It is also routed in a way no designer would choose. Both are true at once, which is exactly what the etiological account predicts: function is a fact about selection history, not about optimal arrangement.

What is actually disputed

Whether functional talk is eliminable.

Eliminativists hold that saying what something is for is shorthand for a causal story, and that a complete account would dispense with it. The reply is that no such account has been produced: biology's explanatory practice is saturated with function talk, and the attempts to paraphrase it out have been longer and less clear than what they replace.

The etiological account is the standard defence and has a known cost. It makes function depend on selection history, so a molecule-for-molecule duplicate of an organism, assembled by accident, would have organs with no functions at all - which strikes many as the wrong result.

The further question is scope. If function talk is legitimate in biology, whether it extends to human institutions, to artefacts, or to history as a whole is where teleology becomes contentious again - and Hegelian and Marxist accounts of history are the cases in point.

Commonly confused with

  • function in the everyday sense The philosophical accounts are attempts to say what makes a function claim true, which ordinary usage takes for granted.

Defined against

  • Chance Whether biological organisation reflects ends or the accumulation of undirected variation is the question natural selection was supposed to settle and did not entirely

Philosophers

Works

Schools

Related concepts

Explanation 1948 · Causation c. 330 BC · Nature c. 330 BC · Flourishing c. 340 BC · Form c. 380 BC

Aristotle's final cause is one of four kinds of explanation and does not require a designer; the seventeenth century's rejection of teleology in physics is often mistaken for a rejection of the whole notion.