Peter Stephen Du Ponceau
Du Ponceau, circa 1830
Born	Pierre-Étienne du Ponceau June 3, 1760 Saint-Martin-de-Ré, France
Died	April 1, 1844 (aged 83) Philadelphia, Pennsylvania, U.S.
Resting place	Mount Vernon Cemetery
Occupation(s)	Philosopher, linguist, jurist

Peter Stephen Du Ponceau (born Pierre-Étienne du Ponceau, June 3, 1760 – April 1, 1844) was a French-American linguist, philosopher, and jurist. After emigrating to the colonies in 1777, he served in the American Revolutionary War. Afterward, he settled in Philadelphia, where he lived the remainder of his years. He contributed significantly to work on the indigenous languages of the Americas, as well as advancing the understanding of written Chinese.

Du Ponceau was born in a French Catholic military-based family. As a child, he lived with his grandmother, aunt, mother, father, younger brother Jean-Michel Du Ponceau and older sister Louise-Geneviéve Du Ponceau. In 1774, his father passed away, and on 1780, so did his mother. Du Ponceau wrote to his sister for 65 years after his departure to America, and his brother attempted to write to him later on, though it is unknown if he was able to reach him. Growing up, Du Ponceau was unloved by his mother, as was quite common in France at the time.^[1]

Du Ponceau's fondness for languages began at a very young age. At the age of 5, Du Ponceau knew both French and Latin by heart. While learning to write, he held extreme fascination with the letters "K" and "W".^[1] He studied at a Benedictine college until he abruptly ended his education after hearing news of severe prosecution of students alike him.^[2] When he was 17, he emigrated to America in 1777 with Baron von Steuben, who was 30 years older. It was speculated at the time that they had been lovers.^[3][4]

Du Ponceau served as a secretary, translator, and interpreter to the Baron von Steuben in the Continental Army during the American Revolution. In 1781, he was forced to return home due to health issues and sudden illness, at the time believed to be consumption.^[2] After the war, he settled in Philadelphia, where he spent the rest of his life. Among his acquaintances were many important figures of the American Revolution, including Alexander Hamilton, John Laurens, Lafayette and James Monroe.^[1]

Du Ponceau joined the American Philosophical Society in 1791 and served as its vice president from 1816 until he became president in 1828, a position he held until his death.^[5] He became notable in linguistics for his analysis of the indigenous languages of the Americas. As a member of the society's Historical and Literary Committee, he helped build a collection of texts that described and recorded native languages. His book on their grammatical systems (Mémoire sur le système grammatical des langues de quelques nations indiennes de l'Amérique du Nord) won the Volney Prize of the Institute of France in 1835.

In 1816, he was elected a member of the American Antiquarian Society,^[6] and in 1820, he was elected a Fellow of the American Academy of Arts and Sciences.^[7]

Du Ponceau also worked on Asian languages and was one of the first Western linguists to reject the axiomatic classification of Chinese writing as ideographic.^[8] Du Ponceau stated:

1. That the Chinese system of writing is not, as has been supposed, ideographic; that its characters do not represent ideas, but words, and therefore I have called it lexigraphic.

2. 

   That ideographic writing is a creature of the imagination, and cannot exist, but for very limited purposes, which do not entitle it to the name of writing.
3. That among men endowed with the gift of speech, all writing must be a direct representation of the spoken language, and cannot present ideas to the mind abstracted from it.
4. That all writing, as far as we know, represents language in some of its elements, which are words, syllables, and simple sounds. In the first case it is lexigraphic, in the second syllabic, and in the third alphabetical or elementary.^[9]

He used the example of Vietnamese, then called "Cochinchinese," which used Chữ Nôm, a modified form of Chinese characters. He showed that Vietnamese used the Chinese characters to represent sound, not meaning. A hundred years later, his theory was still a source of controversy.^[10][11]

He died on April 1, 1844, in Philadelphia, Pennsylvania.

• Dunglison, Robley. A public discourse in commemoration of Peter S. Du Ponceau, LL. D., late president of the American Philosophical Society: delivered before the Society pursuant to appointment, on the 25th of October, 1844. From the Digital Repository of the National Library of Medicine.
• Works by Peter Stephen Du Ponceau, Internet Archive.