Aside from poetry, Milton also wrote prose. His prose works include essays, treatises, tracts and pamphlets that often reflect his social, political, and religious beliefs and opinions. Among his most notable prose works are the essays "Areopagitica," "The Doctrine and Discipline of Divorce," and "A Treatise on Christian Doctrine."
In the 1644 essay "Areopagitica: A Speech of Mr. John Milton for the Liberty of Unlicenc'd Printing, to the Parliament of England," Milton incorporates themes such as freedom of speech and freedom of expression and criticizes the censorship of books and written works. In his 1643 social essay "The Doctrine and Discipline of Divorce, Restor'd to the Good of Both Sexes from the Bondage of Canon Law," Milton discusses the nature of marriage and argues that the most successful marriages and relationships are based on compatability and communication between the partners. In the 1825 theological essay "A Treatise on Christian Doctrine," Milton talks about his religious and philosophical views.
Other notable essays that John Milton wrote include "The Reason of Church-Government Urg'd against Prelaty" (1642); "Of Education" (1644); "The Tenure of Kings and Magistrates, Proving That It is Lawfull, and Hath Been Held So Through All Ages, for Any Who Have the Power, to Call to Account a Tyrant, or Wicked King" (1649); and more. You can find the full bibliography of John Milton here.