The notations used are a bit strange to someone who is a bit used to logic in nonphilosophical problems . But I would say there is one mistake there Second , knowledge entails truth . B Kp pI don ' t see it as obvious . Claims can be true or false , nothing in the definition of operator K forbids to know a false claim . For instance , p p is false . Yet , it is a claim , so the knowability principle says it is knowable . So , Kp p is true . B would state that we can deduce from this that p p is true , which is wrong . I can ' t go much farther than that because they forgot to define what the operator means . <| sep |> I saw one exactly like that on 1 stdibs , but looks like it sold . Only thing similar there now is this f u r n i t u r e c o l l e c t i b l e s b e d s c u s t o m q u e e n p l a t f o r m b edcabinetedwardwormleyidf 3596042 But I ' m not sure you wanna pay $ 18 grand