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what he now calls the “doctrine of right,” also as an a priori science based on definitions.
However, his methodology is much more refined. The following passages bear citing in
whole and commenting on point-by-point.
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 [right], 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
[justice] or upon whom it is practiced. Just so the relation 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 republic
happy, if it comes into being, even if it should never do so. (LL 133) 50
Leibniz’s aim is to establish the a priori foundations of the doctrine of right, i.e., the
principles, methods, and definitions of its basic terms, in advance of fact, independently
of existence. In this sense, “the doctrine of right” is a regulative science. Just as
mathematical notions, such as congruity and proportionality, can be understood without
reference to anything existing, so can definitions of the just and justice. Although he says
that justice consists in congruity and proportionality, he does not go on here to define it in
those terms. His purpose for making the analogy with mathematical notions is only to
assert that just as the mathematical sciences depend on “eternal truths,” so does the
science of right. 51
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
Plato called an idea, and which, when expressed in words, is the same as a
definition. (LL 133) 52
The idea that eternal truths are conditionalia means that they are the necessary conditions
for derived truths, or are the standards by which existent truths are to be measured. For
example, the true definition of the just, whatever it is, expresses an idea. When this is
known, and insofar as the laws of a State conform to it, then its laws will always be just.
50
A.6.1.460: “Doctrina Iuris ex earum numero est, qvae non ab experimentis, sed definitionibus, nec à
sensum, sed rationis demonstrationibus pendent, et sunt, ut sic dicam, juris non facti. Cum enim consistat
Iustitia in congruitate ac proportionalitate qvadam, potest intelligi justum aliqvid esse, etsi nec sit qvi
justitiam exerceat, nec in qvem exerceatur, prorsus ut numerorum rationes verae sunt, etsi non sit nec qvi
numeret nec qvod numeretur, et de domo, de machina, de Republica praedici potest, pulchram, efficacem,
felicem fore, si futura sit, etsi nunqvam futura sit.”
51
Leibniz makes a nearly identical argument some 30 years later in Meditation on the Common Notion of
Justice, as we will see in Chapter Six.
52
A.6.1.460: “Qvare mirum non est harmum scientiarum decreta aeternae veritatis esse, omnia enim
conditionalia sunt, nec tradunt, qvid existat, sed qvid suppositam existentiam conseqvatur: Nec à sensu
descendunt, sed clara distinctaqve imaginatione, qvam Plato Ideam vocabat, qvaeqve verbis expressa idem
qvod definitio est.” It should be noted that Leibniz’s usage of “imaginatione” here is rather strange, since
for Plato, as well as Leibniz, something imagined is always partly sensible.
56