Telling one from another …

… Bullshitting and Lying - by William F. Vallicella,

The bullshitter is one who 'doesn't give a shit' about the truth value of what he is saying. He doesn't care how things stand with reality. The liar, by contrast, must care: he must know (or at least attempt to know) how things are if he is to have any chance of deceiving his audience. Think of it this way: the bullshitter doesn't care whether he gets things right or gets them wrong; the liar cares to get them right so he can deceive you about them.