On this day:
1966 – The Vatican announces the abolition of the Index Librorum Prohibitorum (“index of prohibited books”), which was originally instituted in 1557.
The Index Librorum Prohibitorum (English: List of Prohibited Books) was a list of publications deemed heretical, anti-clerical or lascivious, and therefore banned by the Catholic Church.
The 9th century witnessed the creation of what is considered to be the first index, called the Decretum Glasianum, but it was never officially authorized. Much later, a first version (the Pauline Index) was promulgated by Pope Paul IV in 1559, which Paul F. Grendler believed marked “the turning-point for the freedom of enquiry in the Catholic world”, and which lasted less than a year, being then replaced by what was called the Tridentine Index (because it was authorized at the Council of Trent), which relaxed aspects of the Pauline Index that had been criticized and had prevented its acceptance.
The 20th and final edition appeared in 1948, and the Index was formally abolished on 14 June 1966 by Pope Paul VI.
The aim of the list was to protect the faith and morals of the faithful by preventing the reading of heretical and immoral books. Books thought to contain such errors included works by astronomers such as Johannes Kepler’s Epitome astronomiae Copernicanae, which was on the Index from 1621 to 1835, and by philosophers, like Immanuel Kant’s Critique of Pure Reason. The various editions of the Index also contained the rules of the Church relating to the reading, selling and pre-emptive censorship of books—editions and translations of the Bible that had not been approved by the Church could be banned.
Catholic canon law still recommends that works concerning sacred Scripture, theology, canon law, church history, and any writings which specially concern religion or morals, be submitted to the judgment of the local ordinary. The local ordinary consults someone whom he considers competent to give a judgment and, if that person gives the nihil obstat (“nothing forbids”) the local ordinary grants the imprimatur (“let it be printed”). Members of religious institutes require the imprimi potest (it can be printed) of their major superior to publish books on matters of religion or morals.
Some of the scientific theories in works that were on early editions of the Index have long been routinely taught at Catholic universities worldwide; for example, the general prohibition of books advocating heliocentrism was only removed from the Index in 1758, but already in 1742 two Minims mathematicians had published an edition of Isaac Newton’s Principia Mathematica (1687) with commentaries and a preface stating that the work assumed heliocentrism and could not be explained without it. The burning at the stake of Giordano Bruno, whose entire works were placed on the Index in 1603, was because of teaching the heresy of pantheism, not for heliocentrism or other scientific views. Antonio Rosmini-Serbati, one of whose works was on the Index, was beatified in 2007. The developments since the abolition of the Index signify “the loss of relevance of the Index in the 21st century.”
A complete list of the authors and writings present in the successive editions of the Index is given in J. Martínez de Bujanda, Index Librorum Prohibitorum, 1600–1966. A list of the books that were on the Index can be found on the World Wide Web.
Born on this day:
1903 – Alonzo Church, American mathematician and logician (d. 1995)
Alonzo Church (June 14, 1903 – August 11, 1995) was an American mathematician and logician who made major contributions to mathematical logic and the foundations of theoretical computer science. He is best known for the lambda calculus, Church–Turing thesis, proving the undecidability of the Entscheidungsproblem, Frege–Church ontology, and the Church–Rosser theorem.
Alonzo Church was born on June 14, 1903, in Washington, D.C., where his father, Samuel Robbins Church, was the judge of the Municipal Court for the District of Columbia. The family later moved to Virginia after his father lost this position because of failing eyesight. With help from his uncle, also named Alonzo Church, he was able to attend the Ridgefield School for Boys in Ridgefield, Connecticut. After graduating from Ridgefield in 1920, Church attended Princeton University where he was an exceptional student, publishing his first paper, on Lorentz transformations, and graduating in 1924 with a degree in mathematics. He stayed at Princeton, earning a Ph.D. in mathematics in three years under Oswald Veblen.
He married Mary Julia Kuczinski in 1925 and the couple had three children, Alonzo Church, Jr. (1929), Mary Ann (1933) and Mildred (1938).
After receiving his Ph.D. he taught briefly as an instructor at the University of Chicago and then received a two-year National Research Fellowship. This allowed him to attend Harvard University in 1927–1928 and then both University of Göttingen and University of Amsterdam the following year. He taught philosophy and mathematics at Princeton, 1929–1967, and at the University of California, Los Angeles, 1967–1990. He was a Plenary Speaker at the ICM in 1962 in Stockholm. He received honorary Doctor of Science degrees from Case Western Reserve University in 1969, Princeton University in 1985, and the University at Buffalo, The State University of New York in 1990 in connection with an international symposium in his honor organized by John Corcoran.
A deeply religious person, he was a lifelong member of the Presbyterian church.
He died in 1995 and was buried in Princeton Cemetery.
Church is known for the following accomplishments:
His proof that the Entscheidungsproblem, which asks for a decision procedure to determine the truth of arbitrary propositions in a first-order mathematical theory, is undecidable. This is known as Church’s theorem.
His proof that Peano arithmetic is undecidable.
His articulation of what has come to be known as the Church–Turing thesis.
He was the founding editor of the Journal of Symbolic Logic, editing its reviews section until 1979.
His creation of the lambda calculus.
The lambda calculus emerged in his 1936 paper showing the unsolvability of the Entscheidungsproblem. This result preceded Alan Turing’s work on the halting problem, which also demonstrated the existence of a problem unsolvable by mechanical means. Church and Turing then showed that the lambda calculus and the Turing machine used in Turing’s halting problem were equivalent in capabilities, and subsequently demonstrated a variety of alternative “mechanical processes for computation.” This resulted in the Church–Turing thesis.
The lambda calculus influenced the design of the LISP programming language and functional programming languages in general. The Church encoding is named in his honor.
Many of Church’s doctoral students have led distinguished careers, including C. Anthony Anderson, Peter B. Andrews, George A. Barnard, David Berlinski, William W. Boone, Martin Davis, Alfred L. Foster, Leon Henkin, John G. Kemeny, Stephen C. Kleene, Simon B. Kochen, Maurice L’Abbé, Isaac Malitz, Gary R. Mar, Michael O. Rabin, Nicholas Rescher, Hartley Rogers, Jr., J. Barkley Rosser, Dana Scott, Raymond Smullyan, and Alan Turing. A more complete list of Church’s students is available via Mathematics Genealogy Project.
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