Is it? Everyone is a liar sometimes. You'd have to define liar as someone who lies 100% of his life and then he only SAYS, he's a liar. That could just mean that he felt like expressing, that he lies sometimes or that he's ashamed of some lie he told or whatever.
If they told you they are a liar why are you believing them? they are most likely lying and infact telling the truth, which in turn makes that a fallacy because they are not infact lying. This thread is a riddle and a very easy riddle to crack. peace.
Really? Because its impossible to crack, its called a self referencing paradox for a reason. Your answer is wrong because it continues onwards in an infinite loop. if they are not lieing then that means that they are telling the truth, which means that their statement is a lie and so they are lieing, if that's true then they don't lie and that makes their sentence a lie. Its a never ending paradox. Apparently your skills at debate are even worse then your knowledge of logical contradictions. And even simpler form of this paradox is: "This statement is false."
The definition of the liar varies from person to person and from place to place.There are exceptional people in the world that they don't lie but I notice is that those many people who claim that they are not liar they are actually liar.