Why did madison consider the ninth amendment to be the most crucial?
The ninth amendment, created with Federalist 84 in mind, is there so that all other rights not expressly stated are there, rights that might not have been important in 1787 but are important now. If he did consider it to be the most crucial, then it was because the ninth amendment gave the people all the rights they hadn’t thought about/wouldn’t become apparent. The ninth amendment is like the giant elastic clause of the Bill of Rights.