I was reading the first edition of Spinoza's Ethica (published posthumously, 1677). I noticed that it differed in some places from the text currently in circulation.
The Problem of Reference Indication in the Proof of Proposition 5 in Part 1 of Spinoza's Ethica
PROPOSITIO V : In rerum natura non possunt dari duæ aut plures substantiæ ejusdem naturæ sive attributi.
DEMONSTRATIO : Si darentur plures distinctæ, deberent inter se distingui vel ex diversitate attributorum vel ex diversitate affectionum (per propositionem præcedentem). Si tantum ex diversitate attributorum, concedetur ergo non dari nisi unam ejusdem attributi. At si ex diversitate affectionum, cum substantia sit prior natura suis affectionibus (per propositionem 1) depositis ergo affectionibus et in se considerata hoc est (per definitionem 3 et axioma 6) vere considerata, non poterit concipi ab alia distingui hoc est (per propositionem præcedentem) non poterunt dari plures sed tantum una. Q.E.D.
Here it is written "(per definitionem 3 et axioma 6)". However, in the first edition of Spinoza's Ethica, it is written the following.
(Spinoza 1677a: 4)
In the first edition of Spinoza's Ethica, it is written "(per Defin. 3. & 6.)". The word "axiom" is not found in the same passage.
If you look at the proof of Proposition 5 before and after "(per Defin. 3. & 6.)", you will see that it only mentions the consideration of substances and their modifications, but there is nothing related to the "Idea vera (true idea)" of Axiom 6. Therefore, in terms of content, it is Definition 6 that is closely related to the consideration of substances and their modifications, not Axiom 6. This means that the word "axiom" may have been mistakenly added to the text, and Spinoza's Ethica has been published many times in the past.
Spinoza's Ethica, the first Dutch (translated) edition, 1677.
The first Dutch (translated) edition of Spinoza's Ethica was published at the same year as the Latin (original) edition of it.
(Spinoza 1677b: 4)
In the first Dutch edition of Spinoza's Ethica, it is written "(volgens de derde en zeste[zesde] Bepaling)". Also, the word "axiom" is not found in the same passage.
At least in both the Latin (original) and Dutch (translated) editions of Spinoza's Ethica published in 1677, the word "axiom" was not found in the Proof of Proposition 5 in Part 1, so the text as it is now circulating must be subject to correction.