Para vs. para que with subject shift
In the English word of the day thread for lamb I wrote the following sentence:
Lamb is one of the four land animals that my wife is willing to eat, and because of this I always try to make sure that she does not see a living one, so that I can continue to eat them.
El cordero es uno de los cuatro animales terrestres que mi esposa está dispuesta a comer, y por eso siempre trato de asegurarme de que ella no vea uno vivo, así que yo pueda seguir comerlos.
and was corrected to:
El cordero es uno de los cuatro animales terrestres que mi esposa está dispuesta a comer, y por eso siempre trato de asegurarme de que ella no vea uno vivo, para yo poder seguir comiéndolos.
This was not by one of our normal correctors, but it was by someone whose Spanish is presumably correct.
No comments on the “seguir comerlos” to “seguir comiéndolos” correction please, I was clearly wrong. 
My question is on the “para yo poder”.
In my very simplistic way of thinking (simple works best for me):
If I am following a preposition with a verb:
If there is no true subject change (the subject is obvious)- I follow directly with an infinitive.
If there is a clear subject change then I add “que” after the preposition and conjugate, determining whether I need subjunctive or not (always subjunctive after “para que”).
So I would have written:
… de que ella no vea uno vivo para poder seguir comiéndolos - ..that she does not see a living one so that she can continue eating them.
… de que ella no vea uno vivo, para que yo pueda seguir comiéndolos- that she does not see a living one so that I can continue eating them.
So how does my simplistic approach need to be modified in order to account for “para yo poder”, and is it wrong to do it the way my simple rule tells me.
A link to a good discussion that actually addresses my specific question would be fine.
(My apologies to the Vegetarians among us for revisiting this, I don't think I won any points with them for this in the first place). 
5 Answers
Hi Stadt,
We might try breaking up your sentence into manageable chunks to make it easier to see how its component parts are functioning.
El cordero es uno de los cuatro animales terrestres que mi esposa está dispuesta a comer, y por eso siempre trato de asegurarme de que ella no vea uno vivo, para yo poder seguir comiéndolos.
First let's notice that we have two complete ideas being linked by the conjunction "y"
(1). El cordero es uno de los cuatro animales terrestres que mi esposa está dispuesta a comer
(2) por eso siempre trato de asegurarme de que ella no vea uno vivo, para yo poder seguir comiéndolos.
Since we are only concerned with a particular construction found in the second portion of our sentence, we will disregard the first portion for now.
For the sake of simplicity, we might also find it helpful to remove the expression "por eso" :
Siempre trato de asegurarme de que ella no vea uno vivo, para yo poder seguir comiéndolos.
At this point, if you still find the expression confusing, it is likely the change in subject in the phrase "de que ella no vea uno vivo" (which acts as a complement to the verb "asegurar") is what is throwing you. If this is the case, let's examine the effect of exchanging this expression for a more generic one such as:
Siempre trato de asegurarme de eso para (yo) poder seguír haciéndolo ? I always try to make sure about that in order to be able to continue doing it.
If we wished, we could even take it a step further by reducing the two verb phrase to:
Siempre trato de hacer algo para poder seguir haciéndolo
and then
Siempre hago algo para poder hacer algo
Here, we have reduced our clause to its bare minimum, and in this form perhaps it might be clearer to see that in essence we are simply saying:
I always do something in order to be able to do something
In this case, the words "something" substitute for the more specific phrases used in the original, yet by reducing the sentence to its bare essentials, we (hopefully) can see how the originally rather complex sentence does indeed boil down to an expression in which we see no change in subject.
Hi Stadt, nice thoughtful question.
First of all, I think I would start with emphasizing the 'que' instead of the 'para'. The significance of the use of 'que' is that it introduces a new clause, which will have its own subject and verb. Usually, this new clause is introduced because there is a new subject, in fact if there is a change of subject one has to use que to introduce the new clause.
If the subject of both clauses is the same, you would generally use para + inf. Although I am not sure if it is technically correct to use para que + clause, I think in practice it happens. In your example, the introduction of the somewhat unnecessary subject pronoun 'yo' confuses things, and to my ear using it in front of the infinitive seems weird. However, I am not a native speaker.
The situation is somewhat analagous, for example, to other examples of independent clause / dependent clause construction. For example, when using creer:
Creo que estoy listo. OR Creo estar listo. I would opt for the first construction, even though the subject is the same in both clauses. BUT
Quiero ir, not Quiero que (yo) vaya.
I am not sure whether there is a reason that I prefer creo que + clause but quiero + inf, but that's what I generally encounter.
So, I tried to answer your question and ended up just asking another one. Damn.
How interesting that yo can be used after para. I can see that, too, though. It emphasizes "I" in the para clause, but as there is still no subject change between the two clauses...I guess para + yo + unconjugated verb works.
I doubt that I am all that fit to comment on the relative prevalence or acceptability of this sort of construction; however, there is some evidence for its use on the Internet:
From an article published in the on-line journal Primera Hora, written by Puerto Rican Journalist Maribel Hernández Pérez:
Le pedí a Dios que me diera algo para yo tener un aliento y un motivo para vivir y viene mi hermana con la noticia de que está encinta...
From an article published in the on-line version of the Venezuelan journal el Nacional, written by journalist Gloria M. Bastidas
Para yo tener acceso a ese bienestar tengo que convertirme en un agente revolucionario.
This is an interesting thread on WR.
You will see , Stadt, that the native not only confirms the structure but he even says this is just another way of saying exactly what you said
por que no se dice:"para (mi)poder entender"? saludos
Se me ocurre que es porque es una forma distinta de decir: "Para que (yo) pueda entender".
I am still debating though whether to send you to the dunce corner for that infinitive
It would be nice for a Spanish native to confirm it's correct though. It is certainly a construction I've never seen, but it does also seem to make sense at the same time.
