Lying and bluffing are both modes of misrepresentation or deception. Now the concept most central to the distinctive nature of a lie is that of falsity: the liar is essentially someone who deliberately promulgates a falsehood. Bluffing, too, is typically devoted to something false. Unlike plain lying, however, it is more especially a matter not of falsity but of fakery. This is what accounts for its nearness to bullshit. For the essence of bullshit is not that it is false but that it is phony. In order to appreciate this distinction, one must recognize that a fake or a phony need not be in any respect (apart from authenticity itself) inferior to the real thing. What is not genuine need not also be defective in some other way. It may be, after all, an exact copy. What is wrong with counterfeit is not what it is like, but how it was made. This points to a similar and fundamental aspect of the essential nature of bullshit: although it is produced without concern with the truth, it need not be false. The bullshitter is faking things. But this does not mean that he necessarily gets them wrong.
... Telling a lie is an act with a sharp focus. It is designed to insert a particular falsehood at a specific point in a set or system of beliefs, in order to avoid the consequences of having that point occupied by the truth. This requires a degree of craftsmanship, in which the teller of the lie submits to objective constraints imposed by what he takes to be the truth. The liar is inescapably concerned with truth-values. In order to invent a lie at all, he must think he knows what is true. And in order to invent an effective lie, he must design his falsehood under the guidance of that truth.
On the other hand, a person who undertakes to bullshit his way through has much more freedom. His focus is panoramic rather than particular. He does not limit himself to inserting a certain falsehood at a specific point, and thus he is not constrained by the truths surrounding that point or intersecting it. He is prepared, so far as required, to fake the context as well. This freedom from the constraints to which the liar must submit does not necessarily mean, of course, that his task is easier than the task of the liar. But the mode of creativity upon which it relies is less analytical and less deliberative than that which is mobilized in lying. It is more expansive and independent, with more spacious opportunities for improvisation, color, and imaginative play. This is less a matter of craft than of art. Hence the familiar notion of the "bullshit artist." ...
What bullshit essentially misrepresents is neither the state of affairs to which it refers nor the beliefs of the speaker concerning that state of affairs. Those are what lies misrepresent, by virtue of being false. Since bullshit need not be false, it differs from lies in its misrepresentational intent. The bullshitter may not deceive us, or even intend to do so, either about the facts or about what he takes the facts to be. What he does necessarily attempt to deceive us about is his enterprise. His only indispensably distinctive characteristic is that in a certain way he misrepresents what he is up to.
This is the crux of the distinction between him and the liar. Both he and the liar represent themselves falsely as endeavoring to communicate the truth. The success of each depends upon deceiving us about that. But the fact about himself that the liar hides is that he is attempting to lead us away from a correct apprehension of reality; we are not to know that he wants us to believe something he supposes to be false. The fact about himself that the bullshitter hides, on the other hand, is that the truth-values of his statement are of no central interest to him; what we are not to understand is that his intention is neither to report the truth nor to conceal it. This does not mean that his speech is anarchically impulsive, but that the motive guiding and controlling it is unconcerned with how the things about which he speaks truly are.
It is impossible for someone to lie unless he thinks he knows the truth. Producing bullshit requires no such conviction. A person who lies is thereby responding to the truth, and he is to that extent respectful of it. When an honest man speaks, he says only what he believes to be true; and for the liar, it is correspondingly indispensable that he considers his statements to be false. For the bullshitter, however, all these bets are off: he is neither on the side of the true nor on the side of the false. His eye is not on the facts at all, as the eyes of the honest man and the liar are, except insofar as they may be pertinent to his interest in getting away with what he says. He does not care whether the thing he says describe reality correctly. He just picks them out, or makes them up, to suit his purpose.
Harry Frankfurt, On Bullshit (2005: 51-56)