To understand teleology, you first have to remove from your mind everything you may know about William Paley and the watchmaker, and anything relating to Paley such as Intelligent Design theory. The two versions of teleology are only etymologically related. With Paley, teleology is imposed from the outside, like a watchmaker who creates a watch. The parts of a watch have no inherent tendency to come together and function as a watch; the watchmaker imposes that order on them from outside. That is how Paley's teleology works. Aristotle's teleology is different: the teleology is located inside each thing. This cannot be emphasized enough. Every molecule of Paley must be purged from you mind before reading the rest of the article.
II. Four Causes
Aristotle's theory is that an explanation of a thing requires knowing four different aspects of it:
- Where it came from: it's efficient cause
- What it's made out of: it's material cause
- Its shape and structure: it's formal cause
- What it does: it's final cause
III. Aiming at a Specific Effect
Unlike with Paley, final causality does not directly indicate a designer. The only thing involved in final causality is that any cause which produces an effect produces that one effect (or range of effects) specifically, rather than just any effect. The formula could be written as:
- X causes A, B, and C, but it aims at A specifically over B or C in virtue of its structure
- A volcano causes a magma eruption, pyroclastic flow, mudflows, bird migrations, and burnt trees, but its telos is the magma eruption. It aims at that specific effect over the others, due to its structure. The other effects are accidental.
- A heart causes the pumping of blood and thumping noises, but it aims at pumping of blood specifically in virtue of its form and structure; the thumping noises are accidental.
- An electron orbits the nucleus of an atom, but never attaches itself to the nucleus itself. In virtue of its negative charge, it is directed towards that specific effect (as well as a few others).
Aristotle thought that final causes were just a brute fact of nature. Aquinas, in following Aristotle, thought otherwise and provided an argument for the existence of God: the Fifth Way. However, there is nothing about final causality per se that demands a designer, unlike William Paley's teleology.
V. Science Purges Formal and Final Causes
During the Enlightenment, philosophers such as Descartes, Bacon, Hobbes, Locke, as well as scientists such as Galileo and Newton, decided that science would best be served by focusing only on what can be mathematically quantified. In Aristotelian terminology, this would be material and efficient causes: matter and motion. Formal and final causes were purged from the new scientific revolution, because they are not quantifiable. This new philosophy was called mechanism: there are no final causes; there is just matter pushing against other matter. Like the parts of a watch. Which brings us to...
VI. Teleology After the Purge
So now you can see where William Paley's teleology fits into the picture. Post-Enlightenment, the world consists of meaningless matter that doesn't do anything specific. It's like the parts of a watch. And like the parts of a watch, if there is any order, it must be imposed from outside the system. This is the polar opposite of Aristotle's teleology, who would say that the world is not like a watch and that teleology (final causality) is inherent in the universe.