The Founders left two possibilities open for altering The Constitution. One would be through amendments and the second is through Article 5 "Convention of States" . ----What they did not authorize was SCOTUS or other activist judges to be able to change the Constitution on their own. ---It should be noted that most of the Founders were evolving or had evolved into anti-slavery positions and this includes many of the ones who had held slaves. It took some time and The Civil War for The Constitution to finally be amended to abolish slavery.