Let's say you have an idea that you want to present in writing. For an argument to be valid, it must have supporting evidence. An argument would just be useless if it did not have any documents or laws that would be supporting its justification. To say for example, I wanted to argue that the law of conservation of energy is not true. If I don't show actual evidence of energy being created, then that would leave me with an unclear, and most possibly invalid argument.
