Behind most political scientists' studies of nonvoting there is, implicitly at least, a theory of passive consent. This is particularly the case where nonvoting as a result of apathy is concerned. For, it is suggested, apathy tends to increase when citizens are satisfied that their interests will not be seriously harmed, regardless of which party wins. In other words: the very reasons which underlie apathetic nonvoters' failure to participate in an election testify that their inactivity is a form of passive consent to the election's outcome.
Passive consent, however, cannot be equated to the “theory of consensus” which economists have recently contributed to political science. This “theory of consensus” deals with the “welfare economics” problem of aggregating individual citizens' preferences into a “true”—indeed, into a mathematically precise—schedule of social preferences. Thus, while it is plausible that a citizen can, by nonvoting, tacitly consent to a given electoral outcome, it is also likely that the final social decision would change, however slightly, if in fact this citizen's true preferences had been admitted through voting into the social aggregation. In this case, the final choice would have popular consent without real popular consensus.
The converse can also be true. For example, while Duncan Black's Theory of Committees and Elections and Kenneth Arrow's Social Choice and Individual Values are characterized by a most impressive formal elegance, it is also true that neither makes provision for nonvoting.