Which comes first: philosophers' opinions or arguments?

I think, therefore I am. This was the only thing Descartes was certain of and did not have any other notions of truth at that point. Everything was blank. From that point he rationally created opinions about the world. So you could say he had arguments followed by an opinion and not an opinion followed by arguments. (This is at least as how I interepreted this and my mind could have adjusted this idea to fit my 'opinion' better..) However, I believe that is something very hard to do as all our life we have been taught what is good and what is bad; what I see is that most people have an opinion or feeling about something first and try to back that up with a arguments. Or for example, many arguments follow from the discussion of tax raise/drop but most come down to one point: is it beneficial or detrimental to me, and I take that side of the discussion. But it is difficult to, after being formed into the person you are, to create blank sheets and think everything over from point zero in order to have real rational ideas without bias, where you balance each point in order to come to an opinion. And I feel it is certainly the better thing to do and every time a new perspective comes along you could add this in your reasoning and possibly adjust your opinion. This certainly keeps you openminded!