The preamble of the constitution was ambiguous at the time of the drafting of the constitution, but as changes have been made to the constitution over time through the amendment process the meaning has become clearer. The first way that the constitution allows for change is in Article 1 Section 8. In this section it states that congress is able, "To make all laws which shall be necessary and proper for carrying into execution the foregoing powers, and all other powers vested by this Constitution in the government." This may seem that congress has been given a lot of power, and at this time this was somewhat intentional. The framers did not want to give the executive branch so much power that he was able to oppress the will of many with the power to veto laws. Eventually the system of checks and balances has been utilized more because congress has the power to impeach the president.
The elastic clause was meant to be ambiguous because at the time of the drafting of the constitution the framers could never foresee that topics and conflicts that would rise in regards to the constitution. The clause allows for the growth of the government. The "necessary and proper" clause goes back to the feeling of the framers not wanting to give a lot of power to the president, because this clause gives congress to act. The government is very much so a system of enumerated powers. A perfect example of this lies within Section 2 of Article 2. This section outlines the specific roles of the president. It says that the president is the commander of the armed forces and has the power to appoint justices and ambassadors after consulting with the senate. The main function of the "necessary and proper" clause is to give congress the power to act. On the other hand some may see this as an opportunity for congress to overstep its bounds. The balance of power helps nullify this occurrence somewhat. .
On the subject of the role that an energetic government should play, both Madison and Jefferson offer very valid and varying viewpoints.