"On Bullshit" (2005), by philosopher Harry G. Frankfurt, is an essay that presents a theory of bullshit that defines the concept and analyzes the applications of bullshit in the contexts of communication. Frankfurt determines that the bullshit is speech intended to persuade (a.k.a. rhetoric), without regard for truth. The liar cares about the truth and attempts to hide it; the bullshitter doesn't care if what they say is true or false, but rather only cares whether or not their listener is persuaded.
Frankfurt originally published the essay "On Bullshit" in the Raritan Quarterly Review journal in 1986. Nineteen years later, the essay was published as the book On Bullshit (2005), which proved popular among lay readers; the book appeared for 27 weeks on The New York Times Best Seller list, and was discussed on the Daily Show with Jon Stewart. In the event, On Bullshit (2005) was the foundation for his analogous follow-up book On Truth (2006).