Jacques Rueff · 1922
Jacques Rueff’s 1922 essay, prefaced by C. Colson, argues that morality and political economy can be treated with the same rational discipline as geometry, mechanics, and physics. Its central problem is the scandal, for a scientific mind, of moral philosophy: many systems, nearly identical practical conclusions, and demonstrations that seem to begin from undefined entities. Rueff’s answer is not that moral sciences must imitate physics from outside, but that all sciences already share one structure: empirical laws are first extracted from experience, then “causes” are constructed by definitions and axioms so that deduction can recover those laws.
Il n'y a pas une science, mais des sciences, toutes de même nature, et qui toutes utilisent une méthode rigoureusement unique
English translation: There is not one science, but sciences, all of the same nature, and all of which employ a rigorously single method.
The first part establishes the epistemological machinery. Rueff reduces rational activity to identity/non-contradiction and causality, then treats language, logic, and mathematical analysis as increasingly precise instruments for preserving non-contradiction. Words cut the flow of thought into exchangeable units; formal logic and analysis are not mirrors of things but devices for transforming propositions. This is why Rueff repeatedly insists that science begins only when experience is expressed.
La machine à raisonner, c'est l'ensemble des règles qui permettent la construction de raisonnements en accord avec le principe de non-contradiction.
English translation: The reasoning machine is the set of rules that permit the construction of arguments consistent with the principle of non-contradiction.
The second part applies this view to the “physical” sciences. Geometry begins in practical measurement, mechanics in conventions of length, time, and reference axes, physics in the construction of entities such as forces, atoms, energy, or molecules. Rueff’s key move is to deny that causal order is simply read from nature. Measurement conventions are chosen so that phenomena can be made intelligible under causal form.
Ce principe est bien, ainsi, un habit que nous avons imposé au monde
English translation: This principle is indeed, then, a garment that we have imposed upon the world.
Thus scientific “truth” is neither uncritical realism nor arbitrary fiction. A theory is valid when its deduced consequences coincide with empirically stated laws; when they do not, definitions and axioms must be altered. Rueff’s formula for this process is the book’s conceptual center:
Dans tous les cas, l'édification d'une science est bien ainsi une « création des causes ».
English translation: In every case, the building of a science is thus indeed a "creation of causes."
The third part transfers this model to psychology, morality, and economics. Moral facts are not actions but representations of the “devrait être”: rules such as not killing, lying, or stealing. Moral theories—religious, sentimentalist, Kantian, hedonist, utilitarian—are “géométries morales,” systems of axioms designed to recover these practical rules. Rueff’s Euclidean/non-Euclidean analogy is decisive: a theory may be logically coherent and yet not describe the present moral or social world. Immoral doctrines, Wilsonian international morality before a true society of nations, or socialist economics under existing conditions can be rational but “non-euclidean.”
Dire qu'une théorie morale est vraie, c'est une affirmation qui n'a aucun sens.
English translation: To say that a moral theory is true is an assertion that has no meaning whatever.
This does not produce skepticism, but a stricter criterion: a moral or economic theory is “good” when it explains the known empirical rules of its age and society. Rueff’s historicism enters here. Moral and economic laws do not all operate at once; they depend on the state of social life. Revolutions, slavery’s abolition, market forms, and political institutions change which laws apply, though not the logical possibility of older laws returning under older conditions.
Economics is the most developed moral science in Rueff’s account. He treats price measurement like physical measurement, defines an ideal unit of value, and sketches a mathematical economics based on need, utility, exchange, supply and demand, and production. Economic laws are statistical laws of aggregates, not laws of isolated persons.
Il n'y a pas plus d'économie politique de l'individu que de thermodynamique de la molécule.
English translation: There is no more a political economy of the individual than there is a thermodynamics of the molecule.
The relevance of the work lies in this analogy: rational economics can found political art just as physics founds engineering. To know laws is not to submit passively to them, but to act through them.
L'art politique sera, à l'économie politique mathématique, ce que l'aéronautique est à la physique.
English translation: The political art will be to mathematical political economy what aeronautics is to physics.
Rueff’s conclusion is a disciplined constructivism. Science does not reveal metaphysical essences; it creates conceptual causes that make empirical regularities deducible. Moral science, therefore, must state its empirical laws, define its axioms, deduce rigorously, and test every theorem against life. Its uncertainty is precisely the uncertainty of geometry once experience changes. The final image is of science following, not commanding, reality: life advances, and reason continually rebuilds the causes by which it can think it.
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