Truth

How do you know if something is true? Everybody lies. I'm not just trying to mimic House. Everybody has some grievance with another person, but why must it all be lies. If you know a person lies, how do you know that they are not lying to you? I'm not trying to say all people are bad, but how do you know if something is true or not. How do you know that you are not the one that is hated or lied to? I value the truth and find it very important in everyday life. I wonder what the world would be like if people could only say the truth.