Why should a thesis first be stated before developing an argument?

It shouldnt as in true scientific strategy of thought first u have an idea test the idea to show re occurring results to produce a THEORY then try t disprove your theory thru Null hypothesis, but if thru systematic observation, measurement, and experiment, and formulation of ideas, testing, and modification of the hypotheses stands against experimentation u may say it is proven ,
an argument has nothing t do with scientific thought an argument is without science and is objective. theories are evolved thru subjective scientific research .so we explore our environment gaining more knowledge of the world...
though thru argument by definition we just disagree ......what is proposed infront of us without reason but just to argue what we believe without evidence so a thesis and argument are by definition incongurous as a theory should b stated before a hypothesis, and arguments are left for fools who want to believe and argue the x files are real : )