In an open economy such as the United States, an increase in saving due to, for example, an increase in the federal budget surplus may not result in an equivalent increase in domestic investment.
An increase in saving never results in and increase in domestic investment. 
mnli hypothesis: An increase in saving never results in and increase in domestic investment.  premise: In an open economy such as the United States, an increase in saving due to, for example, an increase in the federal budget surplus may not result in an equivalent increase in domestic investment.