Which provision is the heart and soul of the Constitution?

While there are many important sections to the Constitution, I would say that articles one, two, and three make up the heart and soul of the Constitution, as these articles focus on the concept of separation of powers. Article I deals with the legislative branch. This is a very long section that details the structure of Congress. It also explains how long each term of office is for an elected official, the qualifications a candidate must have in order to run for office, and what powers belong to Congress. It also states that any bill raising revenue must start in the House of Representatives.
Article II deals with the executive branch. It explains who can run for President, and what qualifications a person must have in order to run for that office. It outlines the duties and responsibilities of the President. It also explains how a president can be removed from office.
Article III deals with the judicial branch. It explains the role of the various courts and explains what kinds of cases the courts may hear.
These three articles deal with each branch of the government. The branches of the government are a very important part of the Constitution. The concept of separation of powers, a key cornerstone of the Constitution, is clearly evident as a result of these three articles. In my opinion, these articles make up the heart and soul of the Constitution.
http://constitutionus.com/