One of the most salient features of our culture is that there is so much bullshit. Everyone knows this. Each of us contributes his share. But we tend to take the situation for granted. Most people are rather confident of their ability to recognize bullshit and to avoid being taken in by it. So the phenomenon has not aroused much deliberate concern. We have no clear understanding of what bullshit is, why there is so much of it, or what functions it serves. And we lack a conscientiously developed appreciation of what it means to us. In other words, as Harry Frankfurt writes, 'we have no theory'. Frankfurt, one of the world's most influential moral philosophers, attempts to build such a theory here. With his characteristic combination of philosophical acuity, psychological insight, and wry humor, Frankfurt proceeds by exploring how bullshit and the related concept of humbug are distinct from lying. He argues that bullshitters misrepresent themselves to their audience not as liars do, that is, by deliberately making false claims about what is true. In fact, bullshit need not be untrue at all. Rather, bullshitters seek to convey a certain impression of themselves without being concerned about whether anything at all is true. They quietly change the rules governing their end of the conversation so that claims about truth and falsity are irrelevant. Frankfurt concludes that although bullshit can take many innocent forms, excessive indulgence in it can eventually undermine the practitioner's capacity to tell the truth in a way that lying does not. Liars at least acknowledge that it matters what is true. By virtue of this, Frankfurt writes, bullshit is a greater enemy of the truth than lies are.

法兰克福在《论扯淡》里，劈头就是一句结论：在我们的文化里，最突出的特征之一就是：有太多的人在“扯淡”。虽说扯淡无处不在，却没有一种学说，一个理论来剖析他，他的主旨不在于提供一个理论模型来解析扯淡，而是探讨现今社会何以充斥着言不由衷的扯淡。文中，作者以哲学的辨证方式，开宗明义地区别了“扯淡”与“说谎”。扯淡不是说谎，却是真理最大的敌人。因为说谎的人知道何者为真，却讲的是假话。而扯淡的人既不关心何者为真，也不关心何者为假，只在乎自身利益。这种认为无论事实真相如何都没有差别的态度，就是扯淡的本质。法兰克福在书中将矛头直指当今社会，他指出，扯淡之所以充斥我们的社会，与当代民主社会和市场经济里的种种扭曲不无干系，它助长了扯淡的膨胀，特别是在政治、道德和宗教等分配权益的关键领域，在那里既难以有真伪的辨别，而追求真伪辨别又有风险和麻烦。靠扯淡来搪塞、敷衍、扭曲、误导遂成为权宜之计，更有蔚为主流的趋势。