The Constitution has survived for so long largely for two reasons. First and foremost, it is incredibly difficult to amend. As a previous educator has pointed out, the Constitution has only been amended 27 times in all. This is no accident. The framers of the Constitution feared radical change and so wanted to make it as difficult as possible to make amendments. They worried that if the Constitution could be tinkered with too easily then its whole nature would change, leaving the American system of government with a much weaker foundation.
That explains why the bar for the ratification process is set so high. Each proposed amendment must be approved by two-thirds of the Senate and House of Representatives and three-fourths of the states. By anyone's standards, these are very difficult hurdles to surmount, as supporters of the Equal Rights Amendment have found to their cost.
The second main reason for the Constitution's endurance is its ability to adapt to changing circumstances. For critics, it hasn't adapted anywhere near enough, as the example of the Equal Rights Amendment shows. Nonetheless, it has, at various points in American history, proved possible to amend the Constitution without altering its fundamental nature.
The balance between maintaining a fundamental constitutional bedrock while also accommodating changes in society has always been a very difficult one. But it's that very balance, and the sometimes passionate debates it inspires makes the Constitution a living, breathing document that still speaks to millions of Americans today and will continue to do so for generations to come.