The NYT ran an a piece by Hugo Dixon that boldly proclaimed that if Alex Tsipras, the prime minister of Greece is rational, he will get tough with his left-wing supporters and impose more austerity measures. This is an interesting notion of rationality.
Greece's economy has shrunk by more than 25 percent since 2008. Its unemployment rate is close to 25 percent. The current projections from the I.M.F. and others show little improvement in these numbers by the end of the decade if it sticks to this austerity path. By contrast, if it breaks with the euro its goods and services would suddenly become far more competitive in the world economy as their price would fall due to a lower valued currency. It would also no longer have to run primary budget surpluses since it would be able to avoid payments on its debt for a period of time.
While this break would undoubtedly lead to a short-term hit to the economy as it put its new currency place and worked out patchwork arrangements on trade, it is likely that it would bounce back quickly. The model here is Argentina which went into default in December of 2001. It's economy went into a free fall for three months, then stabilized in the second quarter of 2002. By the fall of the year it was growing rapidly and it continued to grow rapidly for the next five years. It made up all the lost ground before the end of 2003.
It is worth noting that at the time, the I.M.F. and most other "experts" confidently predicted a disaster for Argentina. While there are issues about the accuracy of Argentina's numbers, this has mostly been more a problem in the post-recession period when an over-valued currency and extensive price controls have led to serious economic distortions.
If we want to use the words "tough" and "rational," they would probably better be applied to the strategy of breaking with the euro rather than continuing an austerity policy that promises a level of pain for the Greek period that far exceeds that experienced by the United States in the Great Depression.