On Purpose, by Michael Ruse (Princeton University Press 2017).

I once attended a seminar on the philosophy of laughter, which turned out to be a very grim affair indeed. The event left me with a nagging sense that philosophers might be doing the pursuit of wisdom a disservice by training their intellectual sights on things the townsfolk just know in their bones.

In his new book On Purpose, Michael Ruse, a highly regarded philosopher of science and professor at the University of Florida, could at first glance appear guilty of a similar misdemeanour.

Most people, after all, seem pretty content with the notion of purpose, its place in their lives and the existential disquiet that pervades in its absence.

Ruse is not one of those people. His crusade is to elevate purpose to its proper status in the world of ideas. His opening gambit is to note a distinction that rarely troubles the layperson but has preoccupied metaphysicians for a good couple of millennia. Why does my thumb hurt? Because I hit it with a hammer. This, explains Ruse, is an example of a cause that exists in the past, something Aristotle called an “efficient cause”.

But what causes me to study journalism, invest in a stock or invite friends to dinner? These causes – Aristotle termed them “final causes” – lie in the future. They are mysterious to Ruse because they can motivate action even when their object never comes to exist. The aspiring journalist might study for a career that becomes obsolete before they even graduate.

The commonsense reader will, no doubt, respond that our purpose-driven, “teleological” behaviour simply stems from the fact we’re conscious beings. We can hold rewards in mind and strive towards them.

Read the full book review in Cosmos magazine here