An argument without documentation is of no use..... If not, blaming others takes place for their survival... How to argue? & steps to argue....

An argument without documentation is of no use.....

Documentation in an argument is must because the opponents will change their words they said and will blame you.... 

So take piece of parer and both should write their statements in argument. So you can question about the above statements.

Note: The written statements should be said by them and approved by respected people

Because an argument is to prove the right and wrong. 

Words spoken in air can be changed because they vanish  but letters on paper cant be vanished or forgotten.