Academic, Philosopher, and Psychologist. He was educated as a theologian, and he became a professor of philosophy. He will be best remembered for his written work, "Geschichte der Logosidee in der christlichen Literatur" (1899), and for his first volume of the first edition of the biographical dictionary "Norsk biografisk leksikon," which was a study of his brother-in-law Kristian Birch-Reichenwald Aars (1868-1917), a noted philosopher. He was born one of three children as Anathon August Fredrik Aall in Nesserby, Norway, to Vicar Niels Anton Aall (1833-1896), and his wife Mathilde Susanne Dahl Aall (1842-1910). His brother was the jurist and Fascist politician Herman Harris Aall (1871-1957). His sister Marna Aall Aars (1873–1948) was married to philosopher Kristian Birch-Reichenwald Aars (1868-1917), from 1895 to 1910. He was educated locally but the family moved a lot while he was still a child due to his father's duty as a parish priest. He finished his secondary school education in Stavanger, Norway, in 1886. He then attended and graduated from the prestigious Royal Frederick University, now the University of Oslo in Oslo, Norway, with the cand.theol or Candidate of Theology in 1892. He then studied religious studies in four European countries from 1893 to 1897, before applying for a position as a professor of church history at the Royal Frederick University, now the University of Oslo in Oslo, Norway, but he was rejected as the assessment committee found that he was "deviating from the faith of our Church," and hence was "unfit" to lecture for priestly candidates. He also studied philosophy in the United Kingdom and experimental psychology in Germany. He was elected as a Member of the Norwegian Academy of Science and Letters in 1898, and he worked as a lecturer at the University of Halle-Wittenberg, or the Martin Luther University Halle-Wittenberg in Halle, Saxony-Anhalt, Germany. He was appointed as a professor of philosophy at the Royal Frederick University, now the University of Oslo in Oslo, Norway in 1908. He was the Dean of the Faculty of Humanities from 1918 to 1921, and a visiting scholar at the Columbia University in New York City, New York, from 1924 to 1925. During his lifetime, he was also involved in temperance work, as well as promoting international peace. Besides, his written works, "Geschichte der Logosidee in der christlichen Literatur" (1899), and the first volume of the first edition of the biographical dictionary "Norsk biografisk leksikon," his other notable works include, the thesis "Über die Wirkung der Wiederholung eines Elementes bei gleichzeitiger Vorführung mehrerer Schriftzeichen" (1903), Philosophische Abhandlunge (1906), Logik (1909), and "Die norwegisch-schwedische Union, ihr Bestehen und ihre Lösung" (1912). He also published works on the history of ideas and also helped create the Department of Philosophy at the Royal Frederick University, now the University of Oslo in Oslo, Norway, which he led until his retirement in 1937. He passed away in Lunner, Norway, on January 9, 1943, at the age of 75, and he was buried in Vestre Gravlund in Oslo, Norway. He was married to Cathrine Antonie Langaard Aall (1863–1926), a daughter of businessman Conrad Langaard (1823-1897), until her death. He married for the second time to Lily Weiser (1898–1987), an Austrian citizen and ethnologist in October 1928. His grandfather, Hans Cato Aall (1807-1862), was a Member of Parliament and Mayor of Hammerfest, Norway. He was the grandfather of noted Norwegian psychologist Lisbeth F.K. Holter Brudal who was born on September 19, 1935. He was also a great-great-great-grandson of Nicolai Benjamin Aall (1739-1798), a businessman, ship-owner, property owner and timber merchant, and a great-great-grandnephew of Niels Aall (1769-1854), an estate owner, businessman and politician, Jørgen Aall (1771-1833), a ship-owner and politician, and Jacob Aall (1773-1844), a politician, historian, landowner and government economist. His private correspondence and notes are kept by the National Library of Norway.