j'en dis vs je dis: the pronoun 'en'

Question

I'd really appreciate it if someone could differentiate between 'je dis' being used instead of 'j'en dis', and vice versa, in the examples below. This question boils down to the role 'en' plays here -- whether it's vital/strictly necessary or simply a way of saying something slightly different (via an invisible de cela at the end of the clauses containing 'en' in the first set below).

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Mais voici ce que j'en dis.

Voilà ce que j'en dis...

Si j'en dis plus, ils me tueront.

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Tu comprends ce que je dis?

Parvenez-vous à croire ce que je dis ?

Tu comprends ce que je dis?

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Merci par avance.

Answer 1

You are on the right track to answer your own question:

simply a way of saying something slightly different (via an invisible de cela at the end of the clauses containing 'en' in the first set )

En is a pronoun that replaces nouns with de, and de cela or de ça (whatever the complement may be) is essentially what is being conveyed in your examples. There would be more specific context, something said before, in the first group of your examples.

An example from BDL:

Si tu as de gros ennuis, il vaut peut-être mieux en parler. (En remplace un complément indirect du verbe : Si tu as de gros ennuis, il vaut peut-être mieux parler de ces ennuis.)

In your second group, there is less defined context to presume, it's more general, but it's also asking about the interlocutor's understanding of the situation. You don't have to have a more specific antecedent. Those questions are almost universal or general in conversation.

Adding context to the second group shows the difference.

-- De la nouvelle loi, je ne veux pas en parler. J'en ai déjà parlé. Tu comprends ce que je dis ?