Mechanism versus teleology

1. Why did Steve go to the store? Because he believes that kale is good for him, and he wanted to buy some.

2. Why did the solar eclipse occur? Because the objects in the solar system were in some previous configuration, and because they are subject to the laws of celestial mechanics.

We use both kinds of explanations in daily life. The first kind of explanation is teleological: it explains the present state of affairs in terms of some goal that somebody wanted to achieve. The second kind of explanation is mechanical (in terms of “efficient” causes). In the early modern period, philosophers such as Descartes argued that only efficient causes would figure in a good scientific account of the goings on in the world. And the ensuing debate still does not seem to be completely settled.

This debate flared up in the mid 19th century in relationship to biology. One might have thought that Darwin’s theory of evolution (1859) showed that biological development can be completely explained by efficient causes. But there was pushback from the vitalists, who believed that mechanical causes could not explain the directionality of evolution.

Niels Bohr’s father, Christian, was introduced to this debate in his Filosofikum class at the University of Copenhagen.