The phrase "such thing" is an expression that can be used to indicate something in a general or abstract way. It can refer to any object, event, idea, or concept without specifying exactly what it is. For example, if someone says "I don't know anything about such things," they are indicating that they have no knowledge of the topic being discussed, whether it be technology, art, politics, etc. The phrase can also be used to express disbelief or incredulity, as in "You expect me to believe that? I don't think so!" In this case, "such thing" is a way of saying "that kind of thing," meaning something that one finds hard to accept as true.