Knowledge vs bullshit

Here http://www.powells.com/tnr/review/2006_11_02 is a review of Harry Frankfurt's new volume On Truth which is the successor to his very successful monograph "on Bullshit." Regarding the latter, the reviewer (Simon Blackburn ) writes:'Frankfurt put his finger on on the esential characteristic of the bullshitter,which distinguishes him from the liar.The latter is concerned to communicate something false as if it is true.The former is iondifferent as to whether what he communicates is true or false,"