During the late 17th century, When the Mighty Spanish Empire ruled the ocean seas and whose armies commanded the respect of all major European powers, this map was created.
This map established historic precedent.
The entire region was once claimed by The Spanish Empire. Note that the Portuguese did once control what is the Malaccas (present day Indonesia and Malaysia) but prior to the Treaty of Lisbon, Portugal and its overseas possessions were part of the much larger global Spanish Empire.
The territory of Sabah and even the Celebes, were claimed by the Spanish Empire as part of LAS ISLAS FILIPINAS.
Notice, all of Borneo is claimed.
When Magellan arrived to the Philippines, in 1521, he claimed not only the Philippines proper, but all islands around and fortwith, to be part of the sovereign Spanish Empire. And all islands were claimed LAS ISLAS FILIPINAS.
So, it is historic precedent that the territory of The Philippines does not only include present day Philippines, but even Sabah, Celebes, all of Borneo and Guam and the Marianas.
The 1st section of the Philippine Constitution declares this so.
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