Invention is an important source of technology, and, to understand invention, one needs a model system or prototype. A candidate model system is the hand tool. Using the hand tool as an example, the authors present a systematic approach to invention, dealing with description, classification, and joining or integrating simpler forms. Heuristics for when to integrate are presented. Finally, the authors introduce a new way of thinking about hand tools: simple spatial transformations applied to an abstract element make possible the (...) re-creation of a large number of tools. (shrink)

In this article, we extend the well-known ‘agreeing-to-disagree’ and ‘no-trade’ results from economics and game theory to international relations. We show that two rational countries should never agree to go to war when war is inefficient and when rationality is common knowledge. We argue that this result might provide one possible explanation for the empirical finding, often referred to as the ‘democratic peace’, that modern democracies rarely go to war with one another. We propose that the informational properties of pluralistic (...) institutions (as opposed to oligarchies or dictatorships) lead to better decision-making by democracies and that democracies are therefore more likely to be the rational actors necessary for the ‘no-war’ result. We discuss empirical evidence in support of this proposition. (shrink)