About the Declaration there is a finality that is exceedingly restful. It is often asserted that the world has made a great deal of progress since 1776, that we have had new thoughts and new experiences which have given us a great advance over the people of that day, and that we may therefore very well discard their conclusions for something more modern. But that reasoning can not be applied to this great charter. If all men are created equal, that is final. If they are endowed with inalienable rights, that is final. If governments derive their just powers from the consent of the governed, that is final. No advance, no progress can be made beyond these propositions.
It's important to note the words Coolidge uses here. He calls the Declaration restful, that makes it a trusty bulwark. This is the opposite of 'progressive' which is constantly on the move.
He points out that since 1776 we've made progress, but that cannot be applied to the great Declaration. I would suspect he is talking about this false narrative that progressives use about technology in order to advance their statist cause.
Inalienable rights are indeed final, and in the next part of this paragraph, Coolidge points out:
If anyone wishes to deny their truth or their soundness, the only direction in which he can proceed historically is not forward, but backward toward the time when there was no equality, no rights of the individual, no rule of the people. Those who wish to proceed in that direction can not lay claim to progress. They are reactionary. Their ideas are not more modern, but more ancient, than those of the Revolutionary fathers.
Which is clear. Moving toward bureaucratic despotism(progressivism) is not moving forward, that's moving backward. The darkness of tyranny is always backward when compared to the light of liberty, no matter how that tyranny is structured, and no matter what words they use to hide their schemes of centralized planning.
"The plans differ; the planners are all alike" - Frederic Bastiat - Economic Harmonies - 1.83
This is what made Coolidge such a great President. He was surrounded by progressives, he heard what they were saying, their attacks on American life, on so called "eighteenth century ideas" of "individualism". But Coolidge says no. He says some things are indeed final, and the Declaration is restful. That's what happens when you reach the pinnacle of something, you stop. Liberty is the pinnacle of mankind, not a bunch of bureaucrats steeped in their own legends of their "expertise", who can tell you how best to run your life.
What makes Coolidge so unique in this respect, the context of these words, is that you don't find much of anything like this prior to him. He had something to answer for, because prior to people like Wilson and Roosevelt, there weren't open assaults upon the American way of life. Not in a major way and on a national scale, anyways. This is part of how Coolidge ends the speech:
No other theory is adequate to explain or comprehend the Declaration of Independence. It is the product of the spiritual insight of the people. We live in an age of science and of abounding accumulation of material things. These did not create our Declaration. Our Declaration created them. The things of the spirit come first. Unless we cling to that, all our material prosperity, overwhelming though it may appear, will turn to a barren sceptre in our grasp.
This is something that progressives turn on it's head. They don't understand the relationship between Liberty and all that has made America great. They believe in this historicism, that it's all about the thought of the current age. That's why Wilson talked about the Constitution as a living document.
And because progressives don't believe Liberty is what makes all things possible, they believe instead that America is the root of all evil, that we have stolen from the rest of the world. Without a realization of the treasure of Liberty, what is left? "Of course America stole it from the rest of the world, there's no other explanation", says the progressive.
So it's no wonder that after the depression of the Wilson era, the "Roaring 20's" follows. It's because Coolidge understood Liberty, and sought to defend it. Whereas the progressives seek to tell you that no, "You didn't build that" you stole it. Liberty and prosperity do stand on their own, without stealing from anybody. Yes, we did build that. We are a free people, and that's what free people do.