Final answer:
The Founders had in mind the many generations of citizens that would follow after them when they mention their 'Posterity.'
Step-by-step explanation:
When the Founders mention their "Posterity," they are referring to the many generations of citizens that would follow after them. The Founding generation believed that good citizenship involved a moral responsibility for good conduct and an acceptance of the nation's political principles. They considered their obligation to secure the blessings of liberty not only for themselves but also for future generations.