A younger colleague made me aware of the fact that the distinction might not be obvious for everyone. Hence, here is a short summary:

A positive apparatus is an apparatus where you find all information about each and every single witness (each manuscript you checked and possibly each relevant edition). A negative apparatus is one in which you only show variants which diverge from the reading you selected in the main text.

As a very easy example, suppose you are putting in the main text the following reading: yan nehāsti na tat kvacit and have only three manuscripts, namely A, B and C.

positive apparatus = lemma: kvacit variants: A, B: kutracit. C: kvacit.
negative apparatus: lemma: kvacit. variants: A, B: kutracit.

I (with many others) recommend a positive apparatus. Why?

• With a negative apparatus, you risk to loose track of the one or the other manuscript.
• With a negative apparatus, you don’t know whether a given manuscript is not mentioned because it agrees with the main text or because, e.g., the relevant folio was missing.

Still, a positive apparatus is not really handy if you have, say, over ten manuscripts. Many editors introduce therefore the siglum “Σ” (or anything similar) meaning “All the other manuscripts”. In the previous example:

lemma: kvacit. variants: A, B: kutracit. Σ: kvacit.

What do other readers use or prefer?