Markets are taken as the norm in economics and in much of political and media discourse. But if markets are superior why does the public sector remain so large? Avner Offer provides a distinctive new account of the effective temporal limits on private, public, and social activity. Understanding the Private-Public Divide accounts for the division of labour between business and the public sector, how it changes over time, where the boundaries ought to run, and the harm that follows if they are violated. He explains how finance forces markets to focus on short-term objectives and why business requires special privileges in return for long-term commitment. He shows how a private sector policy bias leads to inequality, insecurity, and corruption. Integrity used to be the norm and it can be achieved again. Only governments can manage uncertainty in the long-term interests of society, as shown by the challenge of climate change.