A natural law is a statement describing a regularity resting on a physical need, and thus not being able to suffer the least exception. It is resulting from the natural Théologie and the natural Philosophie.

History of a problematic concept

One often speaks about the natural laws ; in fact, if the same cause always involves the same consequence, the similarity is a great “immutable law” which the things would follow.

That poses all the same, formulated thus, the question of the legislator , and can seem to imply a “divine order” imposing with the things a certain behavior. Would the concept of natural law be more nun that scientist? In fact, mathematics gives examples that a “natural” law, can be the consequence necessary of axioms with which it seemed not to have not a report/ratio a priori : what was not that a Conjecture can, with often large and long efforts and a wise choice of axioms, to transform itself into Théorème. There would be then no other divine order only that of the Mathématiques, which indeed presents with the usual idea of God the common points to be timeless , immutable , and out of any contingency .

Another reason for interrogation less carries on the concept of “natural law” itself than on its significance. Causal science does not study it “why” in oneself (possible “ reasons for which” an event occurs, which is spring of the study of the phenomena of emergence studied in Théorie of chaos), but it “how” (the manner whose events proceed). Within the causal framework and various bonds between events in the form of “law summarized are expressed”. This “law” is nevertheless descriptive , and not prescriptive . Some examples:

• Kepler does not decide how the satellites “must” describe their revolution, it notes how , in fact, they do it (See Lois of Kepler).
• Newton shows then how the three descriptive laws established by Képler (mathematical conjecture) can result in a more economic way of a single model (the law of attraction in m'/r ²), which moreover explains additional phenomena without report/ratio a priori obvious, like the tides .
• This law of Newton supposes nevertheless a remote action : how to explain this kind of magic? The answer of Newton is firm: assumptions not fingo (I do not advance assumptions). Or, as Wittgenstein will say it later, That which one cannot speak, it should be concealed .

Einstein (following Minkowski, Lorentz and Poincaré) carries out a readjustment: in the construction industry galiléenne of mechanics, it replaces an assumption that the facts invalidated (addition speeds) by another assumption which, it, is confirmed by the facts (the constancy speed of light in all the reference marks) and redefines all the mechanics which results from this.

Simple change of notation; the events, them, always proceed same manner: reality did not change; we know to describe only best. In short, we do not impose “immutable laws on nature”; these laws exist independently of us, and we are satisfied to give of them descriptions which with measurement of time give an account better of it. Rene Descartes wrote (but in another direction) in the Discourse on Method :

“the first was not to never receive any thing for true, that I obviously did not know it to be such. ”

One could not be authorized Descartes and of his design of the doubt to affirm that no objective reality exists. One can simply put forth the assumption that until new order the ideas that we are made on this reality remain likely, in the light of new facts, to be altered.