Idealisation can serve a purpose—even in fields like physicsby Sameer Rahim / September 1, 2017 / Leave a comment
Kwame Anthony Appiah is one of the world’s leading philosophers and the author of numerous books on ethics, cosmopolitanism and identity, among other subjects. He is currently Professor of Philosophy and Law at New York University and in 2016 delivered the Reith Lectures. In his new book, As If, he discusses the role of idealisation in science, ethics and political philosophy. He spoke to Prospect’s Sameer Rahim.
Sameer Rahim: Philosophy is often thought of as the pursuit of truth. But in your new book, As If, you argue that our perceptions are shaped by worldviews that we know to be false—and that that might not be a bad thing.
Kwame Anthony Appiah: I’m not sure I’d put it quite that way. Of course, our perceptions are shaped by our beliefs, and we know some of our beliefs are false. We just don’t know which ones… otherwise, presumably, we’d abandon them. But the point the book makes is a different one: much of our thinking, in the sciences, in philosophy, in everyday life, proceeds with assumptions we know to be not quite right. Hans Vaihinger, the German philosopher whose work inspired me, gave the example of his own religious life. He didn’t believe in the literal truth of the claim that God exists, but he thought there was much to be said for acting morally as if the Christian God were real. And he saw this as pretty much like the way scientists in his day (the turn of the twentieth century) as in ours, use models in which they make assumptions they know are wrong. In his day, for example, when physicists were trying to explain the way temperature and pressure are related in gases, they built models in which a gas was assumed to consist of a collection of tiny perfectly elastic spheres. They knew that atoms really weren’t like that: but if you assumed they were, you got pretty good predictions and a pretty good understanding of why, when you raise the pressure of a gas, the temperature goes up. When we do this sort of thing in physics we call it idealising: in fact the theory was called the ideal gas theory.
You write, “an idealisation is a useful untruth.” Is that simply because the world is too complicated to comprehend and we need simple ideas?