Notable Deaths on April 21

John Maynard Keynes, 1st Baron Keynes, was an English economist whose writings are considered the basis for the school of thought known as Keynesian economics, as well as its various offshoots. Originally trained in mathematics, he built on and refined earlier work on the causes of business cycles. His ideas, further developed after his death as New Keynesianism, are seen as foundational to mainstream macroeconomics. He has been referred to as the "father of macroeconomics" and is considered one of the most influential economists of the 20th century.

Diosdado Pangan Macapagal Sr., also known colloquially as “Apung Dadong”, was the ninth president of the Philippines, serving from 1961 to 1965. He served as the 5th vice president from 1957 to 1961 under Carlos P. Garcia. He also served as a member of the House of Representatives, and headed the Constitutional Convention of 1970. He was the father of Gloria Macapagal Arroyo, who followed his path as President of the Philippines from 2001 to 2010. Diosdado Macapagal Sr is one of the few presidents with doctoral degrees, earning a Doctors of Civil Law degree and a PHD in Economics degree from University of Santo Tomas.

Jean-François Lyotard was a French philosopher, sociologist, and literary theorist. His interdisciplinary discourse spans such topics as epistemology and communication, the human body, modern art and postmodern art, literature and critical theory, music, film, time and memory, space, the city and landscape, the sublime, and the relation between aesthetics and politics. He is best known for his articulation of postmodernism after the late 1970s and the analysis of the impact of postmodernity on the human condition. Lyotard was a key personality in contemporary continental philosophy and authored 26 books and many articles. He was a director of the International College of Philosophy founded by Jacques Derrida, François Châtelet, Jean-Pierre Faye, and Dominique Lecourt.

Hristo Ivanov Prodanov, also known as Christo Prodanov was a Bulgarian mountaineer. Prodanov was the first Bulgarian to climb Mount Everest, doing it via the most difficult way—the West Ridge—as well as alone and without oxygen. Prodanov was the first person to climb Everest in April, when the weather conditions are generally too bad for an expedition, and also the thirteenth person to climb Everest without using bottled oxygen. Climbing the summit at 18:15 local time, he had to descend overnight and got lost shortly after that. On the next afternoon, he reported he had lost his gloves and soon would be unable to hold the radio button long enough to talk. His body was never found.

Liuvigild, Leuvigild, Leovigild, or Leovigildo was a Visigothic king of Hispania and Septimania from 569 to 586. Known for his Codex Revisus or Code of Leovigild, a law allowing equal rights between the Visigothic and Hispano-Roman population, his kingdom covered modern Spain down to Toledo and Portugal. Liuvigild ranks among the greatest Visigothic kings of the Arian period. He consolidated and expanded Visigothic power by defeating the Suebi, campaigning against the Byzantines in the south, and extending control over Basque territories. His legal reforms repealed prohibitions on intermarriage between Goths and Hispano-Romans, fostering greater unity within the kingdom.

Abū al-Husayn Bajkam al-Mākānī, referred to as Bajkam, Badjkam or Bachkam, was a Turkish military commander and official of the Abbasid Caliphate. A former ghulam of the Ziyarid dynasty, Bajkam entered Abbasid service following the assassination of the Ziyarid ruler Mardavij in 935. During his five-year tenure at the Caliphate's court at Baghdad, he was granted the title of amir al-umara, consolidating his dominance over the caliphs al-Radi and al-Muttaqi and giving him absolute power over their domains. Bajkam was challenged throughout his rule by various opponents, including his predecessor as amir al-umara, Muhammad ibn Ra'iq, the Basra-based Baridis, and the Buyid dynasty of Iran, but he succeeded in retaining control until his death. He was murdered by a party of Kurds during a hunting excursion in 941, shortly after the accession of al-Muttaqi as Caliph. Bajkam was known both for his firm rule and for his patronage of Baghdad intellectuals, who respected and in some cases befriended him. His death led to a void in central power, resulting in a brief period of instability and fighting in Baghdad.

Bardas was a Byzantine noble and high-ranking minister. As the brother of Empress Theodora, he rose to high office under Theophilos. Although sidelined after Theophilos's death by Theodora and Theoktistos, in 855 he engineered Theoktistos's murder and became the de facto regent for his nephew, Michael III. Rising to the rank of Caesar, he was the effective ruler of the Byzantine Empire for ten years, a period which saw military success, renewed diplomatic and missionary activity, and an intellectual revival that heralded the Macedonian Renaissance. He was assassinated in 866 at the instigation of Michael III's new favourite, Basil the Macedonian, who a year later would usurp the throne for himself and install his own dynasty on the Byzantine throne.

Catharina Joanna Maria Halkes was a Dutch theologian and feminist, notable for having been the first Dutch professor of feminism and Christianity, at the Radboud University Nijmegen from 1983 to 1986. A Roman Catholic who was originally schooled in Dutch language and literature, she became active in the women's movement within the church, and gained a measure of notoriety when she was forbidden to address Pope John Paul II during his visit to the Netherlands in 1985. She is considered the founding mother of feminist theology in the Netherlands.

Petrus Apianus, also known as Peter Apian, Peter Bennewitz, and Peter Bienewitz, was a German humanist, known for his works in mathematics, astronomy and cartography. His work on "cosmography", the field that dealt with the earth and its position in the universe, was presented in his most famous publications, Astronomicum Caesareum (1540) and Cosmographicus liber (1524). His books were extremely influential in his time, with the numerous editions in multiple languages being published until 1609. The lunar crater Apianus and asteroid 19139 Apian are named in his honour.

Marcel Janco was a Romanian and Israeli visual artist, architect and art theorist. He was the co-inventor of Dadaism and a leading exponent of Constructivism in Eastern Europe. In the 1910s, he co-edited, with Ion Vinea and Tristan Tzara, the Romanian art magazine Simbolul. Janco was a practitioner of Art Nouveau, Futurism and Expressionism before contributing his painting and stage design to Tzara's literary Dadaism. He parted with Dada in 1919, when he and painter Hans Arp founded a Constructivist circle, Das Neue Leben.

Pope Alexander II, born Anselm of Baggio, was the head of the Roman Catholic Church and ruler of the Papal States from 1061 to his death in 1073. Born in Milan, Anselm was deeply involved in the Pataria reform movement. Elected according to the terms of his predecessor's bull, In nomine Domini, Anselm's was the first election by the cardinals without the participation of the people and minor clergy of Rome. He also authorized the Norman Conquest of England in 1066.

Shakuntala Devi was an Indian mental calculator, astrologer, and writer, popularly known as the "Human Computer". Her talent earned her a place in the 1982 edition of The Guinness Book of World Records. However, the certificate for the record was given posthumously on 30 July 2020, despite Devi achieving her world record on 18 June 1980 at Imperial College, London. Devi was a precocious child, and she demonstrated her arithmetic abilities at the University of Mysore without any formal education.

Pauline Hélène "Polly" Higgins was a Scottish barrister, author, and environmental lobbyist, described by Jonathan Watts in her obituary in The Guardian as, "one of the most inspiring figures in the green movement". She left her career as a lawyer to focus on environmental advocacy, and unsuccessfully lobbied the United Nations Law Commission to recognise ecocide as an international crime. Higgins wrote three books, including Eradicating Ecocide, and started the Earth Protectors group to raise funds to support the cause.

Tancredo de Almeida Neves was a Brazilian politician, lawyer, and entrepreneur. He served as Minister of Justice and Internal Affairs from 1953 to 1954, President of the Council of Ministers from 1961 to 1962, Minister of Finance in 1962, and as Governor of Minas Gerais from 1983 to 1984. He was elected President of the Republic in 1985, but died before he had the chance to take office; the vice-president-elect, José Sarney, took office as president in his place.

Peter Abelard was a French philosopher, logician, theologian, composer, and poet, regarded as one of the most brilliant and controversial theologians of his time. Born at Pallet, near Nantes, he became a popular lecturer in Paris, but his academic career was cut short after his love affair with his student and eventual wife, Héloïse d'Argenteuil. Their relationship and philosophical exchange later became the aspect of his life for which he is best known in history and popular culture.

Sir Muhammad Iqbal was an Islamic philosopher and poet. His poetry in Urdu is considered among the greatest of the 20th century, and his vision of a cultural and political ideal for the Muslims of British India is widely regarded as having animated the impulse behind the Pakistan Movement. The honorific commonly refers to him as Allamah and is widely considered one of the most important and influential Muslim thinkers and Islamic religious philosophers of the 20th century.

Väinö Valtteri Linna was a Finnish author and a former soldier who fought in the Continuation War (1941–44). Linna gained literary fame with his third novel, Tuntematon sotilas, and consolidated his position with the trilogy Täällä Pohjantähden alla. Both have been adapted to a film format on several occasions; The Unknown Soldier was first adapted into a film in 1955 and Under the North Star in 1968 as Here, Beneath the North Star, both directed by Edvin Laine.

Milton "Gummo" Marx was an American vaudeville performer, theatrical agent and businessman. He was the fourth-born of the five Marx Brothers. Born in Manhattan, he worked with his brothers on the vaudeville circuit, leaving the act when he was drafted into the U.S. Army in 1918 during World War I and replaced by his brother Zeppo. He had no desire for an acting career, never appeared in any of his brothers' films, and became a successful businessman.

Nina Simone was an American composer, concert pianist, singer, songwriter, and civil rights activist. Simone's bearing and stage presence earned her the title the High Priestess of Soul. Her music spanned styles including classical, folk, gospel, blues, jazz, R&B, and pop. Her piano playing was strongly influenced by baroque and classical music, especially Johann Sebastian Bach, and accompanied expressive, jazz-like singing in her contralto voice. Rolling Stone named Simone one of the greatest singers on various lists.