Frankfurt begins by dissecting a conversation between Ludwig Wittgenstein and one of his students, wherein the student, recuperating from an illness, described herself as â€˜feeling like a dog that had been run overâ€™, a description which Wittgenstein had termed â€˜Bullshitâ€™. The argument centers over the fact that the student could not possibly know how a run-over dog felt, thus the description was not based on fact. As a term of speech the description may be evocative, but in real terms it was based on a false assumption: that either the speaker or the hearer could relate to the description, when in fact neither could. In this case, according to Frankfurt, the speaker was not lying, as she truly did not feel well, but she was indulging in Bullshit, as the description was not based on either fact or experience.
Frankfurt goes to great length to define Bullshit in descriptive terms, to separate it from its primary constituent components â€˜excrementâ€™ and its source, a â€˜Bullâ€™, the corect combination of which is obviously not properly a term of speech.
When we characterize talk as hot air, we mean that what comes out of the speakerâ€™s mouth is only that. It is mere vapor. His speech is empty, without substance of content. His use of language, accordingly, does not contribute to the purpose it purports to serve. No more information is communicated than if the speaker had merely exhaled. There are similarities between hot air and excrement, incidentally, which make hot air seem an especially suitable equivalent for bullshit. Just as hot air is speech that has been emptied of all informative content, so excrement is matter from which everything nutritive has been removed.
To Frankfurt, Bullshit is not a lie, nor is it truth. For a liar to lie, he or she must believe that they know the truth and intentionally choose to mislead the listener: lying is thus a voluntary act of commission. The Bullshitter, conversely, may not know the truth, but wants the listener to believe that they do. A Bullshitter, therefore, may in fact be telling the truth but is not aware that they are doing so â€“ the lie is that they represent themselves as knowing the truth, whereas the veracity of their statement is secondary.
Frankfurt observes that Bullshit, by its pervasive nature, has become an important part of the daily communication that we all participate in, at least as listeners. The discriminating listener believes that they are able to discern Bullshit, which brings us to a circular argument: the belief in ones ability to detect Bullshit may itself be Bullshit.