English Puritan theologian remembered for his writings on ethics and for debating and writing in favour of strict Calvinism in opposition to Arminianism.

As a student at Cambridge, Ames viewed cardplaying as an offense to Christian living—no less serious than profanity. In 1609 his dispute with the Church of England's customs of conduct came to a head in his sermon attacking what he saw as the debauchery attending the feast of St. Thomas. Obliged to leave England, he sailed in 1610 to Rotterdam. There, in the fisherman's habit donned for the passage, he debated Nicolaas Grevinckhoven (Grevinchovius), minister to the local Arminian Church, on the doctrines of atonement and predestination. The Calvinists emphasized that salvation is limited to those who are foreordained by God to receive it and are not capable of falling out of his grace. The Arminians, on the other hand, believed that all men are capable of receiving God's grace if they are believers and if they fulfill certain other conditions.

Ames, considered triumphant in the debates, became widely known throughout the Low Countries. Subsequently, he entered into written disputes with Grevinckhoven on universal redemption and related questions. He served as an observer at the Synod of Dort (1618–19), at which Arminianism was firmly denounced, and as professor of theology at Franeker, in Friesland (1622–33). Among his more important works are Medulla Theologiae (1623; The Marrow of Sacred Divinity, 1642) and De Conscientia et Ejus Jure vel Casibus (1632; Conscience, 1639). The latter text was considered for many years by the Dutch Reformed Church to be a standard treatise on Christian ethics and the variety of ethical situations faced by believers.