Uhm, Vatican I teaches quite clearly that these first causes CAN be known with certainty through natural reason.  So now you bumble and stumble directly into heresy.

Not quite.  It must be noted that this canon is placed in the category of "revelation", and not in "god creator of all things", or "faith and reason".  

denz 1806 canon 1 - "if anyone shall have said that the one true God, our Creator and our Lord, cannot be known with certitude by those things which have been made, by the natural light of human reason, let him be anathema."

As far as argumentation goes, I think we are going to be arguing over the meaning of the word "certitude".  Does the word certitude as it is used here reflect aristotolean empirical knowing?  Or, does it reflect a different type of knowing not forgetting the fact that this canon falls under the heading of "revelation".  Or, for fun's sake, is it "firm" rather than "soft" certitude like that found in denz 1786 of the council?  

I think the answer is found in the council's teaching about the twofold order of "knowledge"(or certitude), where you will find plenty warnings against philosophy, science, and "knowledge falsely so called", all of which I have read and do not disagree with.   

Lastly, it is not "natural reason".  It is "natural light of human reason".  And, this implies that reason so called can not only trend in one direction(towards God's truth).  And, this it seems to me would be precisely the problem with empirical natural reasoning.  "Eye hath not seen, nor ear heard, neither hath it entered into the heart of man, what things God hath prepared for them that love him".  

Here seems to be an argument against the a posteriori logic of aristotle regarding his four causes.

Why does the tree of knowledge in the midst of the garden exist?  

Does it exist as aristotle might argue for its a posteriori final cause("good to eat"), then next for its formal cause("fair to the eyes"), then next for its material cause("delightful to behold"), then finally for its efficient cause("gave to her husband who did eat").  If you did not pick up on it, the four aristotle a posteriori causes regarding the "why" of the tree of knowledge mirrors the exact order of eve's processing.

Or, conversely, does the tree of knowledge exist for its a priori efficient cause(he who made it), then next for its material cause(to test our "touch")?  Eve said two things, which is interesting.  Because, I have been informed that modern philosophy has reduced the 4 causes down to two, rejecting the final cause and the formal cause from philosophical relevancy.  With that said, let's get back to Eve.  Eve said two things in response to the serpent.  In order, she said,"God hath commanded us"(efficient cause = God) that we should not eat(separate from edibility), and "that we should not touch"(material cause) lest we die.  That makes two causes in a priori anti-Aristotelian order.  

So, if you use aristotle a posteriori logic regarding the tree of knowledge, you are going to be using the logic of the serpent.

If you use a priori logic regarding the tree of knowledge, you will be using the logic of one who wishes to obey God's 1st command to man.