Hi Brendan,
Some experts would agree with you that an infant (someone who does not have, and never has had, the use of reason) could be validly ordained, while it would certainly be as illicit as illicit can be.
On the other hand, it is thought that a man who has had the use of reason and then “lost it” can not be validly ordained unless he had, while sane, at least made an intention to be ordained and did not retract that intention.
Not many people have this set of books but the “Exegetical Commentary on the Code of Canon Law” includes commentary (on canon 1024) that agrees with the two points made above. Therefore, this commentary (and other commentaries) agree with you, I think.
I’ll need to think this over a little more before I can understand it. The conclusion seems to be: a man capable of forming an intention must have made such an intention at some point and not withdrawn it in order to be validly ordained. But, a man (even an infant) who has never been capable of forming an intention can be validly ordained without ever having made any intention to receive ordination…
Perhaps I am confused.
Dan