Silent Cal says it well

Calvin Coolidge was president on July 4, 1926, the 150th anniversary of the Declaration of Independence. On the occasion he gave a speech in Philadelphia. It's well worth revisiting in its entirety, but I do want to call one particular passage to your attention, because it's a reminder of the challenges ahead:

Placing every man on a plane where he acknowledged no superiors, where no one possessed any right to rule over him, he must inevitably choose his own rulers through a system of self-government. This was their theory of democracy. In those days such doctrines would scarcely have been permitted to flourish and spread in any other country. This was the purpose which the fathers cherished. In order that they might have freedom to express these thoughts and opportunity to put them into action, whole congregations with their pastors had migrated to the Colonies. These great truths were in the air that our people breathed. Whatever else we may say of it, the Declaration of Independence was profoundly American.

If this apprehension of the facts be correct, and the documentary evidence would appear to verify it, then certain conclusions are bound to follow. A spring will cease to flow if its source be dried up; a tree will wither if its roots be destroyed. In its main features the Declaration of Independence is a great spiritual document. It is a declaration not of material but of spiritual conceptions. Equality, liberty, popular sovereignty, the rights of man — these are not elements which we can see and touch. They are ideals. They have their source and their roots in the religious convictions. They belong to the unseen world. Unless the faith of the American people in these religious convictions is to endure, the principles of our Declaration will perish. We can not continue to enjoy the result if we neglect and abandon the cause.

We are not nearly as religious people in 2016 as we were in 1926. One ought not conclude that those who are not religious do not have a faith, however. They do. Such faith may not rest upon the principles Coolidge discusses, however. We'd best be checking the roots.