Modern economic growth models show that the equilibrium outcome may depend on agents' beliefs (expectations) rather than on economic fundamentals (history). In this situation, the equilibrium is indeterminate. However, if agents have "almost common knowledge" rather than common knowledge about the economic fundamentals, this indeterminacy vanishes in one of these models, under certain restrictions. In this situation, the unique competitive equilibrium can be influenced by government policy, just as in standard models.