Serena Williams, the most successful tennis player in the Open Era, maintains even she does not know where her serve is going until she lands it.

Something similar transpired in 1776, when the Second Continental Congress took up the matter of declaring independence. Whether or not to do it was still a question, but there were powerful arguments that it already had been done by Great Britain earlier that year, when Parliament blockaded American ports and declared their ships enemy vessels. And declarations of independence were bubbling up from towns and assemblies. In April, the chief justice of the South Carolina Supreme Court declared George III had “no authority over us, and we owe no obedience to him.”

On June 11, Congress appointed a committee of five to draft its own declaration, which included Thomas Jefferson, at 33 the youngest member, and John Adams.

But they still did not know where it would land.

Many years later, Adams would recall that Jefferson tried to delegate the job to him:

“I will not,” Adams said. “You should do it.”

“Oh no!” Jefferson said. “Why will you not? You ought to do it.”

“I will not.”

“Why?”

“Reasons enough.”

“What can be your reasons?”

“Reason first,” Adams said, “you are a Virginian, and a Virginian ought to appear at the head of this business. Reason second, I am obnoxious, suspected and unpopular. You are very much otherwise. Reason third, you can write 10 times better than I can.”

“Well,” said Jefferson, “if you are decided, I will do as well as I can.”

It was more than good enough. Jefferson’s words would endure as the paramount expression of the republic, that all men are created equal and that they are “endowed by their Creator with certain unalienable rights; that among these are life, liberty and the pursuit of happiness.”

In itemizing “a history of repeated injuries and usurpations,” Jefferson included the charge that George III had kept, in the colonies, “a market where MEN should be bought and sold ... suppressing every legislative attempt to prohibit or to restrain this execrable commerce,” and that “he is now exciting those very people to rise in arms among us, and to purchase that liberty of which he has deprived them, and murdering the people upon whom he also obtruded them.”

An embarrassed Congress struck these words of the young slaveholder who had over-egged the custard. In its revised form, without referring to slavery, it postponed one debate with which we are still reckoning, but it erected a signpost.

In 1856, Massachusetts Sen. Rufus Choate, in a rebuke to abolitionists, dismissed the Declaration’s claim of equality as a “glittering” generality – but they had read it correctly. “Glittering generalities?” said Ralph Waldo Emerson. “They are blazing ubiquities!”

That was how Lincoln read it, too. In 1858, he said he would not and could not interfere with slavery as long as it was protected where it existed by the Constitution, which he would be sworn to uphold. As a lawyer, he would do no other thing. But the expansion of slavery was morally wrong as was the whole enterprise in America.

The Constitution was like the rule book. On the fundamental question, it was the Declaration Lincoln invoked. And when, five long years and much dying later, Lincoln at Gettysburg declared the nation “shall have a new birth of freedom,” he surely meant the promise of the Declaration would be redeemed.

It is easy to see hypocrisy in it. It is everywhere we look. But we should not also miss the long-lived promise.