Final answer:
It is true that John Stuart Mill developed a case for individual liberty in his work On Liberty. He proposed the harm principle and advocated for women's rights, making him a significant figure in the development of liberalist thought.
Step-by-step explanation:
John Stuart Mill developed a case for individual liberty; this statement is true. Mill, a towering figure in political philosophy, articulated a robust defense of individual freedom in his seminal work, On Liberty, published in 1859.
He posited that personal liberty is essential to societal progress and that it should be protected from the tyranny of both rulers and majority opinion.
Mill's philosophy centered around the harm principle, which suggests that individuals should be free to do as they please, provided their actions do not cause harm to others.
He also championed the cause of women's rights and advocated for their right to vote, marking him as a progressive thinker of his time.