Counterfactuals and history: Contingency and convergence in histories of science and life

• Counterfactual reasoning has been utilised by both historians and evolutionists to imagine slightly altered historical realities.
• Several recent histories of science have been motivated by Gould's “replaying the tape of life” scenario in order to highlight the contingent nature of the development of science.
• In attempting to create plausible counterfactual histories of science, however, historians are forced to accept a fairly weak role for contingency.

This article examines a series of recent histories of science that have attempted to consider how science may have developed in slightly altered historical realities. These works have, moreover, been influenced by debates in evolutionary science about the opposing forces of contingency and convergence in regard to Stephen Jay Gould's notion of “replaying life's tape.” The article argues that while the historians under analysis seem to embrace contingency in order to present their counterfactual narratives, for the sake of historical plausibility they are forced to accept a fairly weak role for contingency in shaping the development of science. It is therefore argued that Simon Conway Morris's theory of evolutionary convergence comes closer to describing the restrained counterfactual worlds imagined by these historians of science than does contingency.