Varieties of scientific explanation.

Scientific explanations often take one of two forms. The first is instantiation. According to this form, an event is said to be explained when it can be expressed as some particular value of a variable in a general proposition, equation, or law. One example of instantiation in psychology is Stevens' psychophysical law. Another is the matching law in the experimental analysis of behavior. A second form of explanation is a deduction from a covering law. According to this form, an event is said to be explained when its description follows as a valid logical deduction in an argument that has a covering law as one premise and a statement of antecedent conditions as another premise. Examples of covering law explanations in psychology are found in traditional neobehaviorism, which sought to develop laws of behavior so that observed behavioral events could be explained as deductions therefrom. Strictly speaking, neither form of explanation is consistent with behavior-analytic explanations derived from Skinner's radical behaviorism, which emphasize the pragmatic sources and contributions of the verbal behavior regarded as explanatory.