Excerpts from Books and Wikipedia
"Abigail had reason to suspect that Mercy Otis Warren would be sympathetic with her protests. Her brother James Otis had asked as early as 1764, in The Rights of the British Colonies Asserted and Proved, 'Are not women born as free as men?' Since they are, Otis insisted, every woman as well as man possesses a 'right to be consulted' in forming any compact or government. Abigail’s knowledge that some of her friends shared her views strengthened her resolve. After writing to Mercy Otis Warren, she wrote another letter to John. It was inappropriate, she observed, for the Continental Congress to proclaim peace and goodwill toward all men and nations while still 'retaining an absolute power over Wives.' To deliver her coup de grace she selected a weapon from Adams’s own arsenal: 'Arbitrary power is like most other things which are very hard, very liable to be broken.' No matter how wise your laws, she concluded, we women enjoy the power 'not only to free ourselves but to subdue our Masters.' If John Adams never again directly addressed the issue of women’s rights in his letters to Abigail, he did not forget his run-in with her on the subject."