Natural law A statement that expresses

Natural law a statement that expresses generally observed behavior. (1.3)... 

Natural law a statement that expresses generally observed behavior. (1.2) Nemst equation an equation relating the potential of an electrochemical cell to the concentrations of the cell components ... 

Natural law a statement that expresses generally observed behavior. 

Some facts in science hold true consistently. Such facts are known as laws. A law is a statement or mathematical expression that reliably describes a behavior of the natural world. While a theory is an attempt to explain the cause of certain events in the natural world, a scientific law describes the events. 

There seem to be two main characteristics of the logic of law statements. First they are supposed to cover every case in a certain domain of phenomena. Let us refer to this as the universal scope of the law. When exceptions turn up there are strategies for preserving the law by restructuring the domain to which it is germane. Laws are presumed to be conjoined with tacit ceteris paribus conditions. Second, natural law statements are supposed to express a necessity that which a law of nature expresses could not have been otherwise. Let us refer to this feature as the modality of the law. 

A third statement of the second law is based on the entropy. In reversible systems all forces must be opposed by equal and opposite forces. Consequently, in an isolated system any change of state by reversible processes must take place under equilibrium conditions. Changes of state that occur in an isolated system by irreversible processes must of necessity be spontaneous or natural processes. For all such processes in an isolated system, the entropy increases. Clausius expressed the second law as The entropy of the universe is always increasing to a maximum. Planck has given a more general statement of the second law Every physical and chemical process in nature takes place in such a way as to increase the sum of the entropies of all bodies taking any part in the process. In the limit, i.e., for reversible processes, the sum of the entropies remains unchanged. 

A theory, such as the atomic theory, usually involves some idea about the nature of some part of the universe, whereas a law may represent a summarizing statement about observed experimental facts. For example, there is a law of the constancy of the angles between the faces of crystals. This law states that whenever the angles between corresponding faces of various crystals of a pure substance are measured they are found to have the same value. The law simply expresses the fact that the angles between... 

Modality as necessity can usefully be captured in the intuition that the statement in question cannot intelligibly be negated. This intuition can reflect two very different kinds of beliefs or presumptions as to what the function of the law statement could be. R may be that those who hold to the law believe that there is a stable natural mechanism that accounts for the regularity covered by it, as a matter of empirical fact. However, some universal statements are taken to be necessary because their function is not to describe the ways things must be with a pre-given vocabulary, but rather to express a rule which fixes some aspect of the meaning of the descriptive terms that appear in the law . It may be that the law only seems to be about material stuff in the material world. It expresses a semantic rule rather than a putative matter of fact. Newton s Second Law, that the force acting on a body is the product of mass and acceleration, has sometimes been treated as a definition of force as that which produces acceleration. Frederick Waismann once declared that all statements ever uttered by chemists, except the most recent, were necessary truths, since they served to amplify the criteria of identity for the substances in question. 

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