how to refer to the former?

Question

In the following sentence

Cuando era aprendiz asistía un día a una conversación entre su maestro y un parroquiano, en la cual éste mantenía que todos los hombres eran iguales.

éste seems to refer to "the latter". Can I say

Cuando era aprendiz asistía un día a una conversación entre su maestro y un parroquiano, en la cual esa mantenía que todos los hombres eran iguales.

i.e. to use esa to refer "the former"?

Answer 1

Cuando era aprendiz asistía un día (...)

The verb "asistir" should be in simple past tense: "asistió". In this case, using imperfect past tense would be similar to saying: "One day, when he/she was an apprentice, he/she used to attend a conversation...", instead of: "One day, when he/she was an apprentice, he/she attended a conversation..."

Also, a comma is missing between the adverbial syntagma and the next syntagma. It should be written like this: "Cuando era aprendiz, asistió un día..."

en la cual esa mantenía...

Here, you can't use "esa" because of two reasons. First: "maestro" and "parroquiano" are in masculine gender, and "esa" is in feminine gender. Second: if you're referencing el parroquiano, this part of the sentence should be like this: "en la cual este último mantenía..." And if you're referencing su maestro: "en la cual el primero mantenía..." Following the order in which both of them are mentioned. Because they are mentioned together, writing "aquél", "ese" or "él" would be unspecific despite being in singular form.

Answer 2

You are almost there but in fact the former is aquél or one of its forms. Spanish uses the maximum contrast here between this one (the latter, nearest to me) and the one over there (the former, possibly a long way away).