Question

Highlight Jefferson’s restated thesis in the text.

We . . . solemnly publish and declare, That these United Colonies are, and of Right ought to be Free and Independent States; that they are Absolved from all Allegiance to the British Crown, and that all political connection between them and the State of Great Britain, is and ought to be totally dissolved . . . And for the support of this Declaration, with a firm reliance on the protection of divine Providence, we mutually pledge to each other our Lives, our Fortunes and our sacred Honor.

Answer 1

This sounds like an excerpt from the Declaration of Independence, if I had to guess?
Without having to read the entire document, I can assume that the "thesis" or the purpose of the writing will be to declare the independence of the United States from the British Empire.
I think this is best expressed in that very first line "We . . . solemnly publish and declare, That these United Colonies are, and of Right ought to be Free and Independent States". In a simple and straightforward way, this excerpt boldly asserts that the (former) United Colonies are, in fact, Independent States.
That's my interpretation, anyway