The essays contained in this volume derive from a high-level Workshop organized by the Hague Academy of International Law to determine whether the legal fundamentals that were established a century ago remain relevant today or whether they have been affected by the requirements of today's world. The world of a century ago only faintly resembles the world in which we now live, and it is therefore legitimate to ask whether the rules laid down in 1907 respond to the needs of 2007. How can it be disputed that the requirement for peace, law, the settlement of disputes, and humanitarian principles still exists, and even more emphatically than in the past? But given the new constraints with which our world is faced - terrorism, degradation of the environment, the exacerbation of under-development in certain States, and food and energy crises - and given the new imbalances that are appearing around the emerging powers, new forms of development, and the ubiquity of new technologies, there is a clear need for reform. The question is whether, in the name of such requirements, it is now possible to depart from certain principles that can be viewed as fundamental achievements. To what extent do the great achievements dating from the dawn of the last century survive among the rules applicable to the century that is now beginning, without excluding the developments and reforms that are necessary in a world that is so different from the world a century ago?