The Taiwan issue is one of the most important geopolitical challenge of our times. Mainland China keeps on insisting that Taiwan must be reunified with the Mainland, while the US arms Taipei so that it wouldn't happen without a great cost.
In order to examine if Taiwan is part of China, we should ask what is China. Below, Tristan G. Brown, an MIT professor makes this interesting point during his class about the Western Zhou:
He makes the case that China isn't a racial group. While the Hans are a majority, the Mongols and the Manchu have also ruled China and there are lots of different ethnicities in China. Also, most things have changed dramatically during history (food, borders, dresses, the spoken languages...). -Even tea culture, my field of expertise, has changed a lot in each dynasty-.
However, from an historical point of view, there's one thing that has bound the past with the present and that's the written language. Looking at China over its long time span, the one thing that doesn't change are the Chinese characters. We can therefore define China as the place where the elite would be using this writing system to record their thoughts, their information, their history... This writing system is hard to memorize. This helped to exclude those who didn't feel Chinese from learning and using it. So, from an historical point of view, we can say that China is the place where the Chinese characters are adopted as the written language.
Such a definition has the merit that it greatly clarifies the Taiwan question. In this regard, Taiwan may actually be seen as more authentically Chinese than Mainland China, because Taiwan is using the traditional characters, while the Mainland has adopted a simplified version of the Chinese characters!
Under this historically grounded definition, it is easier to understand why leaders in Beijing regard Taiwan as part of China and why reunification has become a central political objective. A unified China always meant peace, power and prosperity, while a divided China meant instability and vulnerability.
This understanding doesn't settle the question of when and how the reunification of Taiwan into China should take place. Ideally, it should happen peacefully as the two straits grow naturally closer over time.
