That the only valuable part of the British constitution is so because the very definition of a republic is an empire of laws, and not of men."The treatise defended bicameralism, for "a single assembly is liable to all the vices, follies and frailties of an individual."[311] Adams suggested that there should be a separation of powers between the executive, the judicial and the legislative branches, and further recommended that if a continental government were to be formed then it "should sacredly be confined" to certain enumerated powers. Thoughts on Government was referenced in every state-constitution writing hall. Adams used the letter to attack opponents of independence. He claimed that John Dickinson's fear of republicanism was responsible for his refusal to support independence, and wrote that opposition from Southern planters was rooted in fear that their aristocratic slaveholding status would be endangered by it.[78]

Massachusetts Constitution
After returning from his first mission to France in 1779, Adams was elected to the Massachusetts Constitutional Convention with the purpose of establishing a new constitution for Massachusetts. He served on a committee of three, also including Samuel Adams and James Bowdoin, to draft the constitution. 