Sustainability, Public Debt and Fiscal Policy

I place here some brief notes on the issue of Sustainability and Public Debt.
I will return on the issue about the notion of comprehensive sustainability in a following post.
For now I start this brief noting that the dynamics of public debt is marked by an inherent instability (represented by the flow of interest payments on a given stock of debt), which may make it unsustainable. Here unsustainability means that a permanently raising debt charges a heavy burden on future generations because taxes will have to rise in the future to pay for it. Unless – as we shall see later – certain conditions were not met.