causal law a statement describing a regular and invariant connection between types of events or states, where the connections involved are causal in some sense. When one speaks of causal laws as distinguished from laws that are not causal, the intended distinction may vary. Sometimes, a law is said to be causal if it relates events or states occurring at successive times, also called a law of succession: e.g., ‘Ingestion of strychnine leads to death.’ A causal law in this sense contrasts with a law of coexistence, which connects events or states occurring at the same time (e.g., the Wiedemann-Franz law relating thermal and electric conductivity in metals).
One important kind of causal law is the deterministic law. Causal laws of this kind state exceptionless connections between events, while probabilistic or statistical laws specify probability relationships between events. For any system governed by a set of deterministic laws, given the state of a system at a time, as characterized by a set of state variables, these laws will yield a unique state of the system for any later time (or, perhaps, at any time, earlier or later). Probabilistic laws will yield, for a given antecedent state of a system, only a probability value for the occurrence of a certain state at a later time. The laws of classical mechanics are often thought to be paradigmatic examples of causal laws in this sense, whereas the laws of quantum mechanics are claimed to be essentially probabilistic.
Causal laws are sometimes taken to be laws that explicitly specify certain events as causes of certain other events. Simple laws of this kind will have the form ‘Events of kind F cause events of kind G’; e.g., ‘Heating causes metals to expand’. A weaker related concept is this: a causal law is one that states a regularity between events which in fact are related as cause to effect, although the statement of the law itself does not say so (laws of motion expressed by differential equations are perhaps causal laws in this sense). These senses of ‘causal law’ presuppose a prior concept of causation.
Finally, causal laws may be contrasted with teleological laws, laws that supposedly describe how certain systems, in particular biological organisms, behave so as to achieve certain ‘goals’ or ‘end states.’ Such laws are sometimes claimed to embody the idea that a future state that does not as yet exist can exert an influence on the present behavior of a system. Just what form such laws take and exactly how they differ from ordinary laws have not been made wholly clear, however.
See also CAUSATION, DETERMINISM , LAW- LIKE GENERALIZATIO. J.K.