Hey Mark. I had to read your post a couple of times, but I don’t think I have what you mean. Sorry.
I’m sure I was unclear in some way, but I’m not sure how, so:
Licit matter = what the priest is supposed to use
Illicit matter = what the priest is not supposed to use
Valid matter = bread that can be confected into the Eucharist
Invalid matter = anything else.
So, a brick is obviously both illicit and invalid, since the priest is not allowed to use it for Mass, and it cannot in fact become the Eucharist. Same goes for a Ritz cracker, a pork chop, a rice cake, or rye bread. They’re not permitted, and if a priest, going against the rules, tried to use them, there would be no sacrament and no Eucharist.
The flip side of these cases is unleavened bread made purely of wheat flour and water, including your standard Communion wafers, which are both licit (because Church rules say a priest may use them) and valid matter (because if he does, the transubstantiation actually takes place).
The third category are things that are illicit (a priest goes against the rules by using them), but nevertheless valid. For instance, unleavened bread made purely of wheat and water, except that a small amount of salt has been added. Is the priest allowed to use it? No, and in fact I think he commits a sin if he does so without just cause (for instance, it’s all that’s available on a desert island, in a concentration camp, etc.). But if he
does use it, the Sacrament is validly confected and, despite, the illicit presence of the salt, the bread becomes Jesus.
So if a priest wants to break the rules (or has to, if he’s in a concentration camp) how far can he go? Using bread with honey or sugar added? Fruit or nuts? Using leavened bread? Mixing some rice flour in with the wheat flour? I’m not a canonist, but my point in quoting
Redemptionis Sacramentum was to say that the standard for validity appears to be, whether the bread “would . . . commonly be considered wheat bread.” So what about a French baguette or a slice of Wonder bread? Valid, I would think.
The issue generally comes up, not because priests want to know how far they can go (except in the island/concentration camp scenario), but because thoughtless priests use illicit matter and laypeople want to know whether they actually received the Sacrament. And it’s important to note that what is licit may depend on the circumstances (if you’re in the gulag and get your hands on a French baguette, go for it), but what is valid does not. Even at Auschwitz, the Mass could not be said with rye bread or a rice wafer.
The standards for liceity (what is permitted by the Church) are, of course, stricter than the standards for validity (what can be used in a pinch), because the Church wants to play it very, very safe since a Sacrament – indeed, the highest Sacrament – is at stake.