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, or attracted much sustained inquiry. In consequence, 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, we have no theory. I propose to begin the development of a theoretical understanding of bullshit, mainly by providing some tentative and exploratory philosophical analysis. I shall not consider the rhetorical uses and misuses of bullshit. My aim is simply to give a rough account of what bullshit is and how it differs from what it is not, or (putting it somewhat differently) to articulate, more or less sketchily, the structure of its concept. Any suggestion about what conditions are logically both necessary and sufficient for the constitution of bullshit is bound to be somewhat arbitrary. For one thing, the expression bullshit is often employed quite loosely — simply as a generic term of abuse, with no very specific literal meaning. For another, the phenomenon itself is so vast and amorphous that no crisp and perspicuous analysis of its concept can avoid being procrustean. Nonetheless it should be possible to say something helpful, even though it is not likely to be decisive. Even the most basic and preliminary questions about bullshit remain, after all, not only unanswered but unasked. So far as I am aware, very little work has been done on this subject. I have not undertaken a survey of the literature, partly because I do not know how to go about it. To be sure, there is one quite obvious place to look — the Oxford English Dictionary. The OED has an entry for bullshit in the supplementary volumes, and it also has entries for various pertinent uses of the word bull and for some related terms. I shall consider some of these entries in due course. I have not consulted dictionaries in languages other than English, because I do not know the words for bullshit or bull in any other language.