Of that way we prefer to tie positivad with the obligatory nature and binding character of the right and not with its effective fulfillment or effectiveness. Straight positive he is then that one that can be applied, or is by the Judge, the Administration or the same citizens. Meaning that in this point there is a coincidence with the concept of sources and is excluded from this concept that one of the right that someday was applied but that no longer it is, prescisamente, effective and it is not applied today, like for example the Roman right. Straight Natural Before expressing any idea that could be defining the contours of the natural right we watch like has been conceived through history, not without first to clarify that this it has been a constant subject throughout the evolution of the legal thing. In Greece It was in Greece where practically all the conceptions were born on the natural right and all the philosophical positions in his against, which later the legal world matured and complemented. The Greeks reflected on this topic when occurring account of the great variety of " rights positivos" , of effective norms contradictories, applied in the different cities been. He would be then that little of norms and the same justice was based simply on the interest or the convenience of imposed those who them? Or, rather, there would not be over them governing principles or advisers that determined the legislation and the same conception of fairness? It is clear that many thinkers assumed positions against the existence of a natural right over the tax by the authority. Trasmaco, declared sophist, had the conviction of which the right and justice was not more than the domination expression of which they showed the power, that by means of those procedures could do what it agreed to them more.