# Gérard Desargues

> French mathematician and engineer

**Wikidata**: [Q152817](https://www.wikidata.org/wiki/Q152817)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Girard_Desargues)  
**Source**: https://4ort.xyz/entity/gerard-desargues

## Summary
Gérard Desargues was a French mathematician and engineer who served in the Kingdom of France and made foundational contributions to geometry, specifically projective geometry. He is best known for establishing Desargues' theorem, a pivotal concept stating that two triangles are in perspective axially if and only if they are in perspective centrally. His work also significantly advanced the fields of stereotomy, linear perspective, gnomonics, and scenography.

## Biography
- Born: [Date and place not specified in source material]
- Nationality: Kingdom of France
- Education: [Not specified in source material]
- Known for: Founding projective geometry and formulating Desargues' theorem
- Employer(s): [Not specified in source material, though identified as military personnel]
- Field(s): Mathematics, Geometry, Engineering, Architecture, Stereotomy, Linear Perspective, Gnomonics, Scenography

## Contributions
Gérard Desargues developed the mathematical framework for **projective geometry**, a type of geometry distinct from traditional Euclidean forms. He formulated **Desargues' theorem**, which defines the relationship between axial and central perspective in triangles. His work extended into practical applications including **stereotomy**, the art and science of cutting three-dimensional solids into particular shapes, which was notably relevant in France. He contributed to **linear perspective**, a system where orthogonals converge toward vanishing points, and **gnomonics**, the science of studying sundials. Additionally, he applied his expertise to **scenography**, encompassing theatre design elements such as lighting, sound, set, and costume design. His theoretical work led to the identification of the **Desargues configuration**, a geometric arrangement of ten points and lines, and the **Desargues graph**, a highly symmetric graph characterized by 20 vertices and 30 edges.

## FAQs
**What were Gérard Desargues' primary professional roles?**
He was a French mathematician and engineer who also served as military personnel within the Kingdom of France. His professional identity spanned architecture, engineering, and the theoretical study of mathematics.

**How did Desargues influence the field of geometry?**
He is credited with pioneering projective geometry, introducing concepts that redefined how geometric figures and spatial properties are understood. His specific theorem regarding triangles in perspective remains a cornerstone of this field.

**Did Desargues work on practical engineering or design problems?**
Yes, his work applied to stereotomy for cutting solids, linear perspective for visual representation, and scenography for theatre design. He also studied gnomonics, focusing on the construction and science of sundials.

**What mathematical structures are named after him?**
Several geometric entities bear his name, including the Desargues theorem, the Desargues configuration of ten points and lines, and the Desargues graph with 20 vertices and 30 edges.

## Why They Matter
Gérard Desargues fundamentally altered the trajectory of geometry by establishing projective geometry as a distinct and rigorous branch of mathematics. Before his work, the study of geometric figures often lacked the unified perspective he introduced, particularly regarding how shapes behave under projection. His theorem regarding triangles in perspective provided a critical link between axial and central perspectives, a concept that underpins modern computer graphics, architectural drawing, and visual arts. Without his contributions to stereotomy and linear perspective, the precision of architectural planning and the realism of theatrical scenography would have developed along a different, likely less mathematically rigorous path. The existence of the Desargues configuration and graph demonstrates the enduring structural legacy of his insights into symmetry and spatial relationships.

## Notable For
- Being a French mathematician and engineer active during the Kingdom of France (987–1792; 1815–1848).
- Formulating Desargues' theorem, a fundamental result in projective geometry.
- Pioneering the field of projective geometry itself.
- Advancing the art and science of stereotomy, particularly in the context of France.
- Developing systems for linear perspective where orthogonals converge to vanishing points.
- Contributing to gnomonics, the scientific study of sundials.
- Applying mathematical principles to scenography, including set and lighting design.
- The naming of the Desargues configuration, a specific geometric setup of ten points and lines.
- The naming of the Desargues graph, a symmetric structure with 20 vertices and 30 edges.
- Having a lunar impact crater named "Desargues" in his honor.
- Being recognized with aliases such as Girard Desargues, Gaspard Desargues, Gerard Desargues, and Jerar Dezarq.

## Body

### Professional Identity and Nationality
Gérard Desargues was a human member of the species *Homo sapiens* who lived and worked within the Kingdom of France. His primary professional identities were those of a mathematician and an engineer. He was also an architect, trained to plan and design buildings and oversee their construction. Additionally, he served as military personnel, indicating a role within an organized armed military force. His work intersected with the broader fields of mathematics and architecture, serving as a professional practitioner of engineering.

### Mathematical and Geometric Contributions
Desargues made significant strides in the branch of mathematics known as geometry, which concerns geometric figures and the properties of space. He is most famous for his work in projective geometry, a specific type of geometry that deals with properties invariant under projection. His most celebrated achievement is Desargues' theorem, which states that two triangles are in perspective axially if and only if they are in perspective centrally. This theorem is a critical component of projective geometry and has a high number of related sitelinks, indicating its importance in mathematical literature.

### Applied Sciences and Design
Beyond pure theory, Desargues applied his knowledge to several practical and artistic disciplines. He worked in stereotomy, defined as the art and science of cutting three-dimensional solids into particular shapes, a field with specific relevance to the country of France. He also contributed to linear perspective, a system where orthogonals converge toward one or more vanishing points, essential for accurate visual representation. His expertise extended to gnomonics, the science that studies sundials, and scenography, which includes theatre design elements like lighting, sound, set, and costume design.

### Legacy and Named Entities
The impact of Desargues' work is immortalized in various mathematical structures and geographical features. The Desargues configuration is a geometric configuration consisting of ten points and lines. The Desargues graph is a highly symmetric graph containing exactly 20 vertices and 30 edges. In astronomy, a lunar impact crater has been named "Desargues" to honor his contributions. His name appears under several aliases, including Girard Desargues, Gaspard Desargues, Gerard Desargues, and Jerar Dezarq, reflecting the historical variations in recording his identity. The Wikipedia title for his entry is "Girard Desargues," and he holds a sitelink count of 49 across various knowledge bases.

## References

1. Integrated Authority File
2. Biographie universelle ancienne et moderne
3. BnF authorities
4. Czech National Authority Database
5. The Fine Art Archive
6. International Standard Name Identifier
7. Virtual International Authority File
8. CiNii Research
9. MacTutor History of Mathematics archive
10. [Source](https://www.persee.fr/doc/rhs_0048-7996_1962_num_15_2_4423)
11. Early Modern Letters Online
12. Great Norwegian Encyclopedia
13. Gran Enciclopèdia Catalana
14. AGORHA
15. Desargues, Gérard
16. Freebase Data Dumps. 2013
17. [Source](http://digitale.beic.it/primo_library/libweb/action/search.do?fn=search&vid=BEIC&vl%283134987UI0%29=creator&vl%28freeText0%29=Desargues%20Girard)
18. archINFORM
19. Mathematics Genealogy Project
20. [Source](https://www.archinform.net/service/wd_aiarch.php)
21. LIBRIS. 2012
22. National Library of Israel Names and Subjects Authority File