Final answer:
John Stuart Mill is the philosopher who wrote 'The Subjection of Women,' advocating for women's rights and criticizing their subordination to men.
Step-by-step explanation:
The philosopher who wrote The Subjection of Women, in which he condemned the subordination of women to men as a chief hindrance to human improvement, was John Stuart Mill. Mill was a celebrated nineteenth-century English philosopher known for his advocacy for individual rights and was an important supporter of women's rights. His essay On the Subjection of Women played a significant and influential role in the women's rights movement of the time.