The second theory about Taiwan's international status is that it was left undetermined. According to the Treaty of San Francisco, which took effect in 1952, Japan officially gave up all rights, title and claims over Taiwan. Yet the treaty did not stipulate who Taiwan would belong to.
Thus, Taiwan does not belong to China, and its international legal status is still undetermined.
The ideal way to resolve this problem is to apply the principle of self-determination of the people stipulated in the UN Charter by holding a national plebiscite under the auspices of the UN and let the people of Taiwan decide. But international and domestic political constraints have prevented this from happening. Therefore, there are still many proponents of this theory today.
The third theory is that Tai-wan's position was undetermined in the past and remains undetermined now. Some say Taiwan is still under the military occupation of the ROC; some say the US has sovereignty over Taiwan because it was the main victor over Japan; still others think sovereignty over Taiwan belongs to the Taiwanese people, but that Taiwan still is not a country because the ROC has not ceased to exist and the Taiwanese government has not declared independence.
This theory is a rigid interpretation of international law, and ignores that the formation and application of international law is dynamic. There have been major developments worldwide since 1952, just as there have been in Taiwan. Taiwan's international position cannot be frozen as if it were still 1952.
As Taiwan's international position has evolved from undetermined to determined, the expression of the Taiwanese collective democratic has played a crucial part in the successes Taiwan has achieved.
Even if Taiwan's position remains undetermined and it continues to be occupied by the ROC, one cannot ignore the reality that the ROC has undergone "Taiwanization" which has changed the nature of its military occupation.
The US never advocated having sovereignty over Taiwan after Japan gave it up at the end of the war. The Taiwan Relations Act treats Taiwan practically as a country.
Since Japan gave Taiwan up, the assertion that sovereignty belongs to all of its residents conforms to the principles of sovereignty being in the people and self-determination enshrined in international law.
Is the ROC extinct? When did it die? Opinions are especially divided on this issue. As Taiwan has evolved into a sovereign nation, it is worth considering whether or not it needs a US-style declaration of independence. Applying to become a member state of the UN using the name "Taiwan" is both in form and substance an active declaration that Taiwan is a sovereign and independent country.
The fourth theory is that Tai-wan has de facto independence, but it still does not have de jure independence.
The standards for differentiating between de facto and de jure independence are quite vague. Is it determined by the quality and size of the countries that recognize the country? Or what degree of universal recognition must be reached before a country has de jure independence? From the examples of the more than 100 countries that have achieved independence over the past half century, this kind of differentiation has become meaningless.