"The Bible says that God is present whenever two or more are gathered in His name. So God is already present at the Mass simply because the faithful have gathered together to honor Him with worship."
Well, there are different degrees, or kinds, or modes, of presence. In the Mass, God is present by virtue of His omnipresence everywhere; by virtue of the proclamation of the Word (Scriptures); by virtue of the gathered believers; by virtue of His presence in each baptized person, whose body is a Temple of the Holy Spirit; and by virtue of Christ's Real Presence in the Eucharist.
An analogy might be helpful. Think of several different examples of a man's wife being present n the room with him:
In each case, the wife is present, but in the first example she is present in a way that makes no difference to her husband, and she is "more present" in each successive instance until the last, which may be the most intense experience of her presence.
In a similar way, God is present everywhere at all times; more present to us when we hear the Gospel proclaimed, or when we pray; most present when we are reverently united to Him in the Eucharist. We Catholics are convinced that the Eucharist is the most privileged form of presence that can be experienced on this earth.
Like marital lovemaking, it is not for everyone, at every time, in every place, but only for consecrated people (I use the word generically, to mean those "set aside" by Baptism); at consecrated times, and usually in consecrated places. It is a foretaste of heaven.
God cannot be "ordered" to transubstantiate the host and wine. No priest has that capacity. So, at most, the host and wine are transformed because God agrees to do so. The words "This is My Body" and "This is My Blood" cannot be more than a respectful, reverent invitation from the priest on behalf of the faithful for God to perform the tranformative act. The fact that the host and the wine are transformed is an entirely free and unconstrained act on the part of God for His own purposes. The fact that they are always transformed is a sign of God's lovingkindness to the community of believers.
Everything here is true enough --- you will never find the Church saying that God is in effect our dog, and comes when we whistle. God is always sovereign. Nevertheless, He has lovingly condescended to make His presence known in outward signs which are called Sacraments. We are convinced that the priest has been given (by God's graciousness) the power to make ("confect") the Eucharist which is His Real Presence in an unparalleled way.
This in no way takes away from the many other ways that God is present. It is the Source and Summit of our Christian life.
"God knows the intentions of each person's heart. It seems reasonable that, if a person receives a consecrated host with dishonest intent, God would know this instantly and cause the holy substance of the host to depart from it."
I can understand how you might suppose that, and even more how you might wish it--- not wanting to see Christ blasphemed by mockers. However, when He walked amongst us, Christ did not evade mocking and spitting, though it is ghastly to think of it. Moreover, Scripture indicates, not that the unworthy do not receive Christ because he "exits," but that they receive His Body and Blood in a way that sins against it, in a way that brings condemnation:
1 Corinthians 11:27
Therefore, whoever eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty of sinning against the Body and Blood of the Lord.
Excellent insights.
Just as a preview, what I meant by “a person receives a consecrated host with dishonest intent” is not what you are taking it to mean. Because of that potential misunderstanding, the scripture you are citing may not apply. However, there is at least one that does.
On the other hand, I need to better understand how the terms transubstantiation and transformed are being defined because I think I am assuming/implying something that may not be there according to Catholic doctrine.
One final thought. As I said to a close Muslim friend one time: “Just because your doctrine does not admit that Jesus was raised from the dead, does not mean that the Creator of the Universe is incapable of doing it.”
Good night.