Magnús Eiríksson (22 June 1806 in Skinnalón (Norður-Þingeyjarsýsla), Iceland – 3 July 1881 in Copenhagen, Denmark) was an Icelandic theologian and a contemporary critic of Søren Aabye Kierkegaard (1813–1855) and Hans Lassen Martensen (1808–1884) in Copenhagen.
Due to his very critical attitude towards the church dogma, especially the dogmas of the Trinity of God and the Divinity of Christ, in contrast to which he stressed (at least in his late work) the essential unity of God and the leadership of Jesus (merely) as prophet and teacher, Eiríksson often was labeled as a “pioneer” or “precursor” to the Unitarian movement in Denmark.
Magnús Eiríksson was born the eldest of the five children of Eiríkur Grímsson († 1812), a farmer, and Þorbjörg Stephánsdóttir († 1841), a pastor’s daughter, in Skinnalón, Norður-Þingeyjarsýsla, on the northeastern tip of Iceland. In 1831, he left for Copenhagen to take the university entrance examination. He then remained in Copenhagen until his death in 1881. Eiríksson studied theology at the University of Copenhagen, where he was deeply influenced by Professor Henrik Nicolai Clausen (1793–1877), who represented a form of theological rationalism which appealed to him. After obtaining his degree in 1837, Eiríksson became a tutor to theology students (manuduktør), among whom he enjoyed considerable popularity.
Unlike to Clausen’s rationalism, Eiríksson was very critical to H. L. Martensen’s speculative theology, which he violently attacked in various publications from 1844 to 1850. His basic point was that faith was based on reason, and “only that which can be accepted by reason can and should be accepted by faith”. Martensen refused to become involved in polemic with Eiríksson, and remained completely silent. This silence so irritated Eiríksson that in 1847 he wrote a letter to King Christian VII denouncing Martensen’s silence as “inexcusable, dishonest and dishonorable” and demanding that Martensen be relieved of his professorship at Copenhagen University. His accusations against Martensen were violent and uncontrolled, but at the same time he also attacked the Government’s alleged absolutism. As a result, the public prosecutor was ordered to institute proceedings against him. With the king’s death in 1848, however, and the general amnesty which accompanied his successor, Frederik VII’s, accession to the throne, these were dropped. Eiríksson’s attack on Martensen harmed himself most, particularly financially, as the students, in sympathy with their famous professor, stopped using Eiríksson as a tutor. His financial situation became particularly bad, and he (at least) twice wrote to Søren Kierkegaard asking for help, but Kierkegaard refused.