In May 1776, while Jefferson was in Philadelphia working on drafts of a constitution for Virginia —
new-modelling the form of Government — George Mason was in Williamsburg doing the same. He crafted his Declaration of Rights and wrote, with James Madison, a separate Virginia constitution.
On 12 June 1776 Mason’s Declaration of Rights was unanimously approved by the Fifth Virginia Convention with only a few changes. Two and a half weeks later, after five days of debate, the Constitution of Virginia was approved on 29 June 1776 — without Jefferson’s input. His constitution had arrived too late to affect the shape of the state government; only the preamble was used — tacked onto the beginning of the Constitution.
What is interesting about these events is the cross-pollination of ideas. Jefferson began work on the Declaration of Independence sometime after 11 June 1776 when the
Committee of Five (John Adams, Benjamin Franklin, Robert Livingston, Roger Sherman, and Jefferson) was appointed by Continental Congress to formally write-out an argument to notify Britain that the colonies were asserting their independence. In parallel, in Williamsburg on 12 June, the Declaration of Rights was passed by the Virginia Convention. Here is Section 1:
That all men are by nature equally free and independent, and have certain inherent rights, of which, when they enter into a state of society, they cannot, by any compact, deprive or divest their posterity, namely, the enjoyment of life and liberty, with the means of acquiring and possessing property, and pursuing and obtaining happiness and safety.
As his previous work towards a Virginia constitution attest, Jefferson was actively engaged in events back home. In fact, he had unsuccessfully tried to get himself released from Congress so he could attend the Virginia Convention. After all, at this point Virginia (like the other 12 colonies) was becoming its own little country, and that is where Jefferson hoped to make an impact.
So he certainly saw a copy of the Declaration of Rights, either before 12 June or after. This is what he wrote in his draft Declaration of Independence:
We hold these truths to be sacred & undeniable; that all men are created equal & independent; that from that equal creation they derive rights inherent & inalienable, among which are the preservation of life, & liberty, & the pursuit of happiness ...
Note how neatly Jefferson uses the word
inalienable to replace Mason’s locution
when they [men] enter into a state of society, they cannot, by any compact, deprive or divest their posterity; and Jefferson uses the word
preservation as a perpetual loop around
life, & liberty, & the pursuit of happiness instead of the stand-alone right to
safety. And: Jefferson ignores the right of property — probably because it is not strictly inalienable.
The point here is that Jefferson did not write the Declaration out of whole cloth. He borrowed; improved.
Near the end of his life, recognizing what he had accomplished, and trying to explain it, Jefferson wrote to Richard Henry Lee (8 May 1825):
This was the object of the Declaration of Independence. Not to find out new principles, or new arguments, never before thought of, not merely to say things which had never been said before; but to place before mankind the common sense of the subject, in terms so plain and firm as to command their assent …