It is mystical Voodoo alchemy. If you believe it's Gold, then it becomes gold even though it's still (by all appearances) lead. Hey, can I sell you a box of lead colored gold bricks? Only $200 an ounce.
I'm confused by why you think your position is "philosophical." Are you saying tht "philosophically" the bread is the physical body of Christ, but in reality it is bread?
I am saying that anything has an essence and an accidental appearance. For example (as suggested by Calvin) a dove appeared to St. John as he baptized Christ but he identified that in essence it was the Holy Ghost (John 1:32).
Likewise, the eucharistic bread has every appearance (accident is the technical term) of bread. A laboratory will only discover bread. A zoologist at the scene in John 1:32 would only see a dove. The essence, or substance, of the bread is body, soul and divinity of Christ.