John Stuart Mill, a prominent 19th-century liberal philosopher, was a staunch advocate for women's suffrage and equality. His arguments, most notably articulated in 'The Subjection of Women' (co-authored with Harriet Taylor Mill), were rooted in his principles of utilitarianism and individual liberty. Mill argued that denying women the right to vote was a violation of their individual freedom and a significant impediment to societal progress.

He contended that women, as rational beings, were fully capable of participating in public life and contributing to political decision-making. Excluding half of the population from political participation not only deprived women of their rights but also deprived society of their talents, perspectives, and potential contributions. Mill believed that the existing legal and social subjugation of women was a relic of a bygone era, based on outdated prejudices rather than reason or justice. He saw women's suffrage as a necessary step towards a more just, rational, and prosperous society, where individual merit, rather than gender, determined one's role and opportunities.