In previous empirical work, the basis for the proposition that democratic c
ountries do not fight each other has been a single equation regression of h
ostility on democracy and other variables. This approach is misleading for
two reasons. First, peace and democracy are part of a simultaneous system o
f relations in which they foster each other. Before quantitative inferences
which affect policy conclusions can be reached, a separate structural equa
tion has to be estimated corresponding to each of these variables. The equa
tions must be distinguishable from one another at the same time as they emb
ody the interdependence between peace and democracy. Second, previous regre
ssion studies emphasized the statistical association between democracy and
peace rather than focusing on the substantive magnitude of that effect. To
demonstrate the sensitivity of the results to these concerns, we accepted t
he data and indexes of one of the most influential statements of the peace-
democracy thesis, and studied the Cold War period where it is deemed strong
est. We differed from the prevailing paradigm by estimating an identified,
simultaneous two-equation interactive system. In this more properly specifi
ed model, the dyadic democracy-peace nexus generally was not statistically
significant and, more important, was very small in its impact. The alternat
ive, peace causing democracy, was much stronger. Neither equation in the si
multaneous system explained more than six per cent of the variance, so that
other factors are likely to be much more important. Deterrence of aggressi
on and patient negotiation of differences may be a more important guide to
public policy than attempts to export western, democratic institutions to o
ther nations.
The analysis of these data show that it is more likely that the most import
ant differences that arise between nations are specific to historic epochs
and their political and socio-economic conjunctures. Various other indices
have been suggested for conflict and democracy in the literature. as well a
s numerous modifications of the additional variables to be included in the
regression equations. The results have tended to be variable with respect t
o these modifications, but the failure of single equation model specificati
ons to deal with the problem of simultaneous causation makes their results
subject to our fundamental methodological criticism and unable to support t
he burden of policy recommendations.