In 2005, Harry Frankfurt’s little book of only 67 pages – On Bullshit -  became a surprise bestseller.

It tapped into public concern about the “spin” surrounding America’s and Britain’s launch of the second Iraq War, but its message resonated beyond particular events.

“Bullshit” surrounds us, says Frankfurt, a professor of moral philosophy at Princeton, but we don’t see it for what it is. That is why we need a theory of it.

Bullshit is similar to “humbug”, which in The Prevalence of Humbug (1985) Max Black defined as “deceptive misrepresentation, short of lying, especially by pretentious word or deed, of somebody’s own thoughts, feelings, feelings and attitudes.”

Bullshit is an attempt to deliberately mislead, yet it stops short of an outright lie. Bullshit can also be pretentious, and a conscious misrepresentation of the way you in fact see a situation.

Both humbug and bullshit aim to create an impression that I am thinking or believing something, even if I have not come out and actually said it. In this gap, therefore, a mistruth can be made without actually stating a lie.

A grand political speech, for instance, does not aim to say how the world actually is. Its purpose is to make the speaker sound like a patriot, or a spiritual person, or a protector of morals.

Frankfurt ultimately concludes that humbug does not fully grasp the real nature of bullshit. To explain why, he quotes Longfellow about the nature of “craft”: In the elder days of art/Builders wrought with greatest care/ Each minute and unseen part/ For the Gods are everywhere.

An old school craftsman is not out to “make an impression”, but rather its opposite: to make sure something is done right, even if no one notices the detail of the work.

In contrast, shoddily made things are bullshit, because time, craftsmanship and care are totally left out of the process. Everything is about a hoped-for short term effect that will benefit the producer. The quality of the good and its durability itself is irrelevant.