Do the bread and wine turn into the body and blood of Christ?

I recently read a high-level exchange about the metaphysics of transubstantiation. On one side was a Protestant philosophy prof. (Kyle Blanchette). I mention that because his argument is the stimulus for this post. I'm not trying to develop his argument. Perhaps the argument in this post is different from how he'd understand his own argument. That's not the purpose of my post. My objective isn't to reproduce his argument. It simply gave me an idea to think about and run with. But I wish to credit the stimulus. 

Transubstantiation is often challenged on philosophical grounds. Philosophy isn't for everyone, but this isn't just an academic issue. Transubstantiation is Catholic dogma. If a single Catholic dogma is false, that falsifies Catholicism at one stroke. 

According to Trent, by the consecration of the bread and of the wine, a conversion is made of the whole substance of the bread into the substance of the body of Christ our Lord, and of the whole substance of the wine into the substance of His blood; which conversion is, by the holy Catholic Church, suitably and properly called Transubstantiation.

And the catechism says 1375 It is by the conversion of the bread and wine into Christ's body and blood that Christ becomes present in this sacrament. 

So the dogma of transubstantiation seems to require that the bread and wine turn into or change into the body and blood of Christ. The unconsecrated communion elements become the body and blood of Christ. That, however, raises the issue of what's required for one thing to become something else. 

Suppose on Monday I see a mouse. Suppose on Tuesday I see a Porsche. Suppose you tell me that the Porsche used to be the mouse. The mouse turned into a Porsche.

A problem with that claim is that, at the level of a mouse and a Porsche, they have nothing in common. They have some constitutive elements in common, like atoms and molecules, but in no respect is a mouse a Porsche. There's complete discontinuity at that higher level. A difference in kind, not degree. 

The Catholic position is actually more radical than my illustration. On the Catholic position, the two substances don't even share any constitutive elements in common (see below). 

Put another way, it's consistent that a Porsche was never a mouse. It was always a Porsche. It didn't originate as a mouse. Consistent for each to have separate origins. 

What really happened is that the mouse ceased to exist, and (let's say) a Porsche suddenly sprang into existence. The mouse didn't become a Porsche. Rather, the mouse existed, then it ceased to exist. The Porsche didn't exist, then a day later it came into being. There's succession but no continuity. No continuum between what was the case on Monday and what was the case on Tuesday. 

But this generates a contradiction between what transubstantiation claims and what it implies. The claim is that the bread and wine turn into the body and blood. But the implication of the dogma is that the body and blood replace the bread and wine. The bread and wine cease to exist. Something else takes their place. So there's no continuity between the two things. 

Given the claim, there's no reason a priest has to start with bread and wine to get the same result. Since the end-result replaces the bread and wine, you could, in principle, have the replacement directly, without the bread and wine as a starting-point, just as you don't to start with a mouse to produce a Porsche. There's no essential relationship between the bread and wine and the replacement. It isn't necessary for a Porsche to be the end-product of a mouse. Indeed, that would be very strange way to create a Porsche.

At this point a Catholic might object that they do share something in common: the secondary properties of bread and wine. The phenomenal/sensory properties of bread and wine.

But that won't do. According to the metaphysics of transubstantiation, those are accidental properties. But at the substantive level, the body and blood share nothing in common with the bread and wine. One substance didn't become or change into another substance. Rather, one substance replaces another substance, but it has the same accidental properties. So the fundamental dichotomy remains.