Hi Trinitas!!!
Actually, it was the great Catholic Anglo-French writer Hilaire Belloc [1870-1953] who counted Islam as a Christian heresy [as well as a threat to the West] in his book, aptly named, "The Great Christian Heresies".
The following website has further information on this:
chestertonandfriends.blogspot.com/…/belloc-islam-is…
Thanks for the welcome ... yes the typhoon was a tad hairy [as we say in Oz!].
Christus vincit Christus regnat Christus imperat
Viva il Papa!

SboC, I was reading your posts and came across the words
“Islam is a Christian heresy” possibly being attributed to
Saint Thomas Aquinas by “Philosopher”. Hopefully, he will
reference the original source for this unusual quotation.

(good to see you back online after the Hong Kong storms)

My dear friend Trinitas, I am not sure where you got that [partial] quote supposedly attributable to St Thomas Aquinas regarding Islam. If you go to this website:
www.catholicapologetics.info/apologetics/islam/thomas.htm
you will see that St Thomas Aquinas did not believe that Mohammed was a true prophet and he cogently argued against the Moslem objections to the Blessed Trinity and the Incarnation. Nowhere, however did he say anything about Moslems not worshipping the same God as the Christians.
Christus vincit Christus regnat Christus imperat
Viva il Papa!

Islam is a Christian heresy
St Thomas Aquinas

I cannot believe that a Doctor of the Church would make
the above statement, and particularly St Thomas Aquinas
who acknowledged that his knowledge of Islam was limited.

Naturally, as you have so rightly enumerated, there are myriad doctrinal differences, of fundamental importance, between ourselves and Moslems [actually, as someone has already mentioned on this website, there are some who have categorised Islam as a "Christian heresy"] this, however, does not negate the simple reality that Yahweh, Allah and God are one and the same Deity. In fact, our Eastern Christian brothers and sisters who use Arabic to pray, refer to God as "Allah" because "Allah" in Arabic simply means "God". Jews also do not believe in the Trinity, nor that Jesus is the Eternal Son of the Father, nor in the Divinity of Jesus ... BUT ... do you then go on to say that Yahweh, the God of the Jews, is not the same God as the One Jesus prayed to in the Garden of Gethsemane in the New Testament ... that Christians do not adore the same God as the Jews?
Since the Catholic Faith has the fullness of truth ... the further a religion is from Catholicism then the further it is from the fullness of truth but both Judaism and Islam do have that most important spark of ultimate truth ... belief in the One True God.
Christus vincit Christus regnat Christus imperat
Viva il Papa!

Islam denies the Trinity:
Certainly they disbelieve those who say: Surely Allah is the third (person) of the three; and there is no god but the one God, and if they desist not from what they say, a painful chastisement shall befall those among them who disbelieve (Sura 5:73).

Islam denies the Father and the Son:
The Christians say: The Messiah is the son of Allah; these are the words of their mouths; they imitate the saying of those who disbelieved before; may Allah destroy them (Sura 9:29-30).
It does not befit GOD that He begets a son, be He glorified (Sura 19:35).

Islam denies the Deity of Christ:
The Messiah, Jesus the son of Mary, was no more than God’s apostle (Sura 4).
They do blaspheme who say: Allah is Christ the son of Mary (Sura 5:72).

Clearly then, the Quran denies:

1. The Trinity;
2. The Sonship of Christ;
3. The Deity of Christ.

The conclusion is inevitable: the god of Islam is not the same God of the Holy Scriptures. Christians do not adore the same God as Muslims. Muslims are not merely ignorant of the Triune nature of God and the Deity of the Son: the Quran explicitly negates the doctrine of Christ as taught in the Bible. Rather than adoring God with us, Muslims pray to their god that he might destroy us because of our faith in Christ, the Son of God. 'The Christians say: The Messiah is the son of Allah; these are the words of their mouths; they imitate the saying of those who disbelieved before; may Allah destroy them' (Sura 9:29-30).

"On September 12th, 2006, Joseph Ratzinger claimed that the god of the Muslims is both transcendental and unreasonable."

Firstly, Pope Benedict would never have referred to "the god of the Muslims" because Jews, Christians and Moslems are all monotheists and all worship the One same God. Secondly, and consequently, the Pope could not have said, and indeed did not say, that this "god ... is ... unreasonable". The point he was very clearly, and correctly, making is that the "understanding" that some Moslems have had [have] of God historically has been [is] unreasonable. A totally different thing. Thirdly, this "Gloria.TV News Brief" seems to imply that there is something wrong with God being "transcendental". It is a common teaching of Jews, Christians and Moslems that God is ultimately transcendent. He is totally "other" for who can understand the mind of God? One of the differences between Christians and Moslems, however, is that for us God is ALSO intimately IMMANENT ... becoming one of us in Our Lord Jesus Christ ... both God and man.
Anyone wanting to know more about the real "Regensberg Address" might be interested in the following website:
en.wikipedia.org/wiki/Regensburg_lecture
One of the wondrous mysteries of our Christian Faith is that God is, at the very same time, both transcendent and immanent. Glory be to God!
Christus vincit Christus regnat Christus imperat
Viva il Papa!

When the Pope criticizes Islam, Muslims murder Catholics in Muslim countries.

"Islam does not allow for intellectual inquiry into the foundations of its belief. The Church must be careful to not say things that poor and defenseless Catholics and Christians living in fear in Islamic states from Indonesia to Pakistan to Egypt will be murdered by a barbaric religion.

The Pope, in this case, is behaving with prudence and caution where other people's lives are at stake. If one had any loved ones in the Middle East, most especially if they were priests or nuns with targets on their backs, we would hope the Pope exercised extreme care in his comments.

The Pope invited the Muslims to a discussion of their tendencies toward violence. They responded by murdering nuns, burning churches, etc. I would say the discussion is finished, and the Pope needs to say nothing more. The discussion is now one for soldiers to conduct, not churchmen.

When the British were in the Middle East (Palestine), Jews and Muslims lived in relative harmony. Once the state of Israel was established, Jews from all over the world immigrated into the region and that is where the trouble began. One cannot deal with radical Muslims and Zionist Jews, so I don't why Pope Benedict is meeting with Hassan al-Banna. The pope better make sure this man is not near a sword.

Despite everything....only the Pope and the Church can save the West from being silently Islamised (if it is to be saved). Don't expect secular governments to lift a finger to oppose Islamisation....quite the opposite.

And if the West goes down to Islam....don't expect any mercy for Christians in Islamic nations.