The Canon of Ptolemy

The Royal Canon of Claudius Ptolemy, a second-century C.E. astronomer, is also used to support the traditional date 587 B.C.E. Ptolemy’s list of kings is considered the backbone of the chronology of ancient history, including the Neo-Babylonian period.

Ptolemy compiled his list some 600 years after the Neo-Babylonian period ended. So how did he determine the date when the first king on his list began to reign? Ptolemy explained that by using astronomical calculations based in part on eclipses, “we have derived to compute back to the beginning of the reign of Nabonassar,” the first king on his list.⁴ Thus, Christopher Walker of the British Museum says that Ptolemy’s canon was “an artificial scheme designed to provide astronomers with a consistent chronology” and was “not to provide historians with a precise record of the accession and death of kings.”⁵

“It has long been known that the Canon is astronomically reliable,” writes Leo Depuydt, one of Ptolemy’s most enthusiastic defenders, “but this does not automatically mean that it is historically dependable.” Regarding this list of kings, Professor Depuydt adds: “As regards the earlier rulers [who included the Neo-Babylonian kings], the Canon would need to be compared with the cuneiform record on a reign by reign basis.”⁶

What is this “cuneiform record” that enables us to measure the historical accuracy of Ptolemy’s canon? It includes the Babylonian chronicles, lists of kings, and economic tablets​—cuneiform documents written by scribes who lived during, or near, Neo-Babylonian times.⁷

How does Ptolemy’s list compare with that cuneiform record? The box “How Does Ptolemy’s Canon Compare With Ancient Tablets?” (see below) shows a portion of the canon and compares this with an ancient cuneiform document. Notice that Ptolemy lists only four kings between the Babylonian rulers Kandalanu and Nabonidus. However, the Uruk King List​—a part of the cuneiform record—​reveals that seven kings ruled in between. Were their reigns brief and negligible? One of them, according to cuneiform economic tablets, ruled for seven years.⁸

There is also strong evidence from cuneiform documents that prior to the reign of Nabopolassar (the first king of the Neo-Babylonian period), another king (Ashur-etel-ilani) ruled for four years in Babylonia. Also, for more than a year, there was no king in the land.⁹ Yet, all of this is left out of Ptolemy’s canon.

Why did Ptolemy omit some rulers? Evidently, he did not consider them to be legitimate rulers of Babylon.¹⁰ For example, he excluded Labashi-Marduk, a Neo-Babylonian king. But according to cuneiform documents, the kings whom Ptolemy omitted actually ruled over Babylonia.

In general, Ptolemy’s canon is regarded as accurate. But in view of its omissions, should it really be used to provide a definite historical chronology?

4. Almagest, III, 7, translated by G. J. Toomer, in Ptolemy’s Almagest, published 1998, page 166. Ptolemy knew that Babylonian astronomers used mathematical schemes to “compute” the times of past and future eclipses because they discovered that eclipses of the same character reoccur every 18 years.​—Almagest, IV, 2.

[Chart/​Pictures on page 30]

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HOW DOES PTOLEMY’S CANON COMPARE WITH ANCIENT TABLETS?

Ptolemy omits some kings in his list. Why?

PTOLEMY’S CANON

Nabonassar

Nabu-nadin-zeri (Nadinu)

Mukin-zeri and Pul

Ululayu (Shalmaneser V) “King of Assyria”

Merodach-baladan

Sargon II “King of Assyria”

First Kingless Period

Bel-ibni

Ashur-nadin-shumi

Nergal-ushezib

Mushezib-Marduk

Second Kingless Period

Esarhaddon “King of Assyria”

Shamash-shuma-ukin

Kandalanu

Nabopolassar

Nebuchadnezzar

Amel-Marduk

Neriglissar

Nabonidus

Cyrus

Cambyses

THE URUK KING LIST AS FOUND ON ANCIENT TABLETS

Kandalanu

Sin-shumu-lishir

Sin-sharra-ishkun

Nabopolassar

Nebuchadnezzar

Amel-Marduk

Neriglissar

Labashi-Marduk

Nabonidus

[Picture]

The Babylonian chronicles are part of the cuneiform record that helps us to measure the accuracy of Ptolemy’s canon

[Credit Line]

Photograph taken by courtesy of the British Museum