Watch your mouth, Irish, and keep your shirt on. Sheesh. :rolleyes:
Pope Leo XIII teaches that when the externals are performed according as the Church does them, we should presume that the minister has the intention to do what the Church does.
However, people can say things they don't intend to say, and do things they don't intend to do. I believe I have experienced this myself.
Now it could be argued that I had fully intended to say _______, but after I said it I repented of myself. This, in a minister would not invalidate the sacrament. But if in fact I meant to say _______, but something else came out instead, then it could be argued that a minister, likewise, could intend not to do what the Church does, but does it anyway.
Just like you might intend to go buy milk after work, but you drive straight home instead, because of an ingrained repetitious pattern of behaviour.