The Summa perfectionis, a Medieval Book on Alchemy

The Summa perfectionis of pseudo-Geber is a Latin book on alchemy which appeared in the 13th or early 14th  century. "Pseudo-Geber" alludes to the fact  that for a long time, the book was believed to be the work of Jabir Ibn Hayyan, or Geber, as he was known in the Latin West. 

 

Today, most or all of the many works on alchemy once attributed to Geber are believed to have been written by others, and it is even disputed whether Geber really existed. 

William R Newman published a critical edition of the Summa perfectionis in 1991, and has argued that it was authored by the 13th-century Franciscan friar Paul of Taranto, a judgement which has come to be widely accepted. 

Paul also published works on alchemy under his own name. Whether it is thought that he published the Summa perfectionis anonymously, and that it later was attributed to Geber, or whether Paul claimed that his own work was that of Geber, I do not know. I also am not expert enough in the position of alchemy, vis a vis the Church authorities of the 13th and 14th century, to hazard a guess as to whether the Summa perfectionis was more objectionable than other alchemical works, which might have made it prudent to claim not to have been its author.

Perhaps Paul attributed the work to Geber, not out of fear of the disapproval of the Inquisition, but because Muslim scholars in general, and Geber, mythical or not, in particular, were highly-esteemed in the Latin West as authorities on alchemy, and Paul hoped to gain more attention with a purported translation of Gerber than he otherwise could have attained. "Alchemy" is an Arabic word, like "algebra" and "zero."

As so often: the key words in the above are "perhaps" and "I do not know." I also don't know exactly when or how the belief in Geber as a real author began to fade. In the late 17th and early 18th centuries some of the many editions of the Summa perfectionis were being published with attribution to Geber without the "pseudo-", and in the 19th century Kopp, Hoefer and others were questioning his authorship, and I can't tell you what came in between.

The Summa perfectionis is written in an admirably clear and direct style, explaining the instruments used by the alchemist, the methods of combining and heating various materials, results thus far attained and future results hoped for -- all remarkably similar, in substance and tone, to a modern textbook of chemistry. Two major differences from modern chemistry were the assumption that all metals were combinations of sulfur and mercury, and the belief that an elixer could transform base metals such as lead into precious metals such as gold. 

But only particularly ignorant modern chemists would claim that science today works with absolutely no false assumptions. People in different times and places saw the world differently than we do, and interpreted data differently. Only those particularly ignorant of those other times and places, or particularly ignorant of our own present, could assume that the present is vastly superior in every way.