Leibniz wrote:
It is obvious that the happiness of mankind consists in two things - to have the power, as far as is permitted, to do what it wills and to know what, from the nature of things, ought to be willed. Of these, mankind has almost achieved the former; as to the latter, it has failed in that it is particularly impotent with respect to itself. For the power of man has certainly increased immensely in the present age, and of the two elements of our earth, one is almost tamed and the other restored from the rapacity of the former. We have spanned the seas by a kind of mobile bridge and so united lands that were once divided by enormous gaps. The heavens themselves cannot defeat us, and when they hide their stars, we find help in deformed bit of glass. And having moved them nearer to us and multiplied our eyes to be admitted into the interior of things and to enlarge the face of the world a hundredfold, we then suddenly have disclosed to us new worlds and new species, both equally admirable - the one in magnitude, the other in smallness.
Nor do we lack glasses [conspicilia] of another kind, by which to survey the scattered bits not merely of space but of time. The light of history has been brought to us, so that we seem to have lived always. A new kind of monument has been prepared - though of paper, yet more enduring even than bronze - by which great geniuses may survive all the injuries of barbarous and tyrannical times and always anticipate the assured immortality of heaven by an imaginary eternity of fame. We have thus embraced time in our writings, the heavens in our telescopes, the earth in travel, and the sea in ships. The other elements follow this example. The air too now reveals its secrets which have been hidden from all eternity …
… Now that we are conquerors of the world, there assuredly remains an enemy within us; everything is clear to man but man, the body to the mind, and the mind to itself. To drop the tragic style and speak more naturally, we are ignorant of the medicine of bodies and of minds. We treat the former as does an agent something for the sake of gain; we treat the latter as a boy does his lesson - as nothing, for he learns it in the hope of forgetting it. It is not surprising, therefore, that until now we have established no science of the pleasant, or the useful, or the just. The science of the pleasant is medicine, that of the useful is politics, and that of the just is ethics …
The doctrine of Right belongs to those sciences which depend on definitions and not on experience and on demonstrations of reason and not of sense; they are problems of law, so to speak, and not of fact. For since justice consists in a kind of congruity and proportionality, we can understand that something is just even if there is no one who practices it or upon whom it is practiced. Just so the relations of numbers are true even if there were no one to count and nothing to be counted, and we can predict that a house will be beautiful, a machine efficient, or a commonwealth happy, if it comes into being, even if it should never do so.
We need not wonder, therefore, that the principles of these sciences possess eternal truth. For they are all conditionalia, conditional truths, and treat not of what does exist but of what follows if existence be assumed. They are not derived from sense but from a clear and distinct intuition [imaginatio], which Plato called an idea, and which, when expressed in words, is the same as a definition. That which can be understood clearly, however, is not always true, though it is always possible; and it is also true, in addition, whenever the only question is that of possibility.
But whenever there is a question of necessity, there is also one of possibility, for if we call something necessary, we deny the possibility of its opposite. It therefore suffices to demonstrate the necessary connections between things and their consequences in this way: by deducing them from a clear and distinct intuition (that is, from a definition when this intuition is expressed in words), through a continuous series of definitions which imply them; that is, through a demonstration.
Therefore since the doctrine of Law is a science, and the basis of science is demonstration, and definition is the principle of demonstration, it follows that we must first of all investigate the definitions of the words Right, just, and justice, that is, the clear ideas by which we usually estimate the truth of propositions or of the right use of words in speech, even when we do not know we are doing so.
The method of our investigation is to gather the more important and distinctive examples of the use of these terms and to set up some meaning consistent with these and other examples. For just as we construct a hypothesis by induction from observations, so we construct a definition by comparing propositions; in both cases we make a compendium of all other instances, as yet untried, out of the most important given cases. This method is necessary whenever it is not desirable to determine the use of terms arbitrarily for one's self.
The Source:
Gottfried Wilhelm Leibniz, ‘Elements of Natural Law 1670-71’, in Gottfried Wilhelm Leibniz Philosophical Papers and Letters, A Selection, translated and edited by Leroy E. Loemker, 2nd ed. Klueger Academic 1989 [pp. 131-133]
Evolutions of social order from the earliest humans to the present day and future machine age.