Let the numbers speak

Although it is often claimed that statistical techniques are ways of lettin g the objective data speak for themselves, in both the contrast and correla tional modes of statistical inference, all the real work is done by the a p riori decisions imported into the analysis-which categories are to be used to create contrasting populations, which categories are to be measured, whi ch categories are to be held constant while others are compared, and which is cause and which is effect? The authors explore here the problem of direc tionality of causation and the relationship between cause and effect, on th e one hand, and dependent and independent variables, on the other. In syste ms of any complexity there are feedbacks-negative and positive feedbacks fo rming loops, embedded in larger contexts and subject to influences that can impinge on the loop at any point, such that the same pair of variables may show positive correlations in some situations and negative correlations in others.