Bullshit is pervasive, yet almost no one had rigorously defined it before this book

Frankfurt opens by observing that everyone recognizes bullshit when they encounter it and freely uses the term, yet almost no sustained philosophical or linguistic effort had gone into pinning down exactly what separates it from other forms of dishonest or careless speech. He treats this gap as a genuine intellectual oversight rather than a trivial curiosity, arguing that a concept this central to how people communicate and evaluate each other's honesty deserves the same careful scrutiny philosophers apply to concepts like truth or knowledge.

His approach is deliberately narrow and analytical: rather than cataloguing every rhetorical use and misuse of bullshit across different contexts, he focuses on identifying the necessary features that make something count as bullshit at all, distinguishing it from adjacent but different phenomena like lying, exaggeration, or simple error. This tight focus is what allows the book, despite its brevity, to arrive at a genuinely sharp and durable distinction.

Takeaway: a phenomenon everyone recognizes casually can still reward rigorous, careful definition.