Today we have many alternative medicines, not a few of which connect back to aboriginal cultures. Some of these alternative medicines were born under the influence of European imperialism, as they were not "alternative" until modern empires and modern medicine came to these distant regions. The present study begins with a broad question: how did conceptions of the relationship between modern Western medicine and traditional local non-Western medicine come to be? To explore the historical origins of these two conceptions, I focus herein on Japanese colonial Taiwan (1895–1945), where modern medicine became dominant while traditional medicine also flourished. My research finds that the historical realities of colonial Taiwan were not reflected in the progressive narrative of medicine. According to this narrative, modern medicine became dominant around the world while traditional medicines were swept into the ash heap of history because only modern medicine was the true, effective science of preventing, diagnosing, and treating physical ailments. The history of colonial Taiwan teaches us a much different lesson: practitioners of traditional medicine there were a significant part of the public health system during the colonial period. For example, they rallied against the plague in the late 19th century, diagnosing and treating patients when antibiotics had yet to be developed. Even so, the island witnessed an institutional medical shift, in which licensed practitioners of modern medicine deified modern medicine and denigrated traditional medicine, labeling the latter "primitive" and "non-medicine." In response, practitioners of traditional medicine produced new narratives aiming to challenge this colonial boundary between medicine and non-medicine. These practitioners' fundamental argument was that traditional medicine, though epistemologically different from modern medicine, was still legitimate medicine. From this effort, we now have the widely held belief today that both modern medicine and traditional medicine are legitimate, but distinct, medicines. This historical outcome of colonial resistance occurred worldwide. In my study, I identify the social, political, and colonial contexts of medical resistance in Japanese Taiwan, revealing their roots in issues related to inequality, distrust, economic affordability, and conceptions of body and health care. / Doctor of Philosophy / In this study, I explore conceptions of modern and traditional medicine through a historical lens, and break down two related myths: the first myth is the progressive narrative of modern medicine, which holds that modern medicine became dominant because of its medical superiority; and the second myth is the narrative held by extremist supporters of traditional medicine, who insist that only millennia-old traditional medicine can resolve human ailments without giving rise to untoward side effects and exorbitant costs. I show that, in the case of Japanese colonial Taiwan (1895–1945), both modern and traditional medicine flourished. The history of colonial Taiwan shows us that modern medicine on the island became dominant for two main reasons: first, the public health system successfully dealt with epidemics, which were the most significant threat to life at that time; and second, the colonial government recognized only modern medicine and labeled traditional medicine a non-medicine despite relying on its practitioners in the pre-antibiotic age. The history of colonial Taiwan also shows us that traditional medicine is not "old wisdom" unchanged for thousands of years. Beginning in the 19th century, practitioners of Taiwanese traditional medicine re-constituted it for colonial consumption, arguing that traditional medicine was also true medicine, though epistemologically distinct from modern medicine. This conception of traditional medicine has since informed many current views of traditional medicine. In 2018, the World Health Organization (WHO) published the eleventh revision of the International Classification of Diseases (ICD-11), which, for the first time, featured a chapter on traditional Chinese medicine covering such topics as diagnostic techniques for Qi, blood, and fluid disorders. This inclusion of traditional medicine into the ICD-11 is a major step forward in this process of medical integration and may help resolve the historical confrontation between modern and traditional medicine. However, the WHO decision limits recognition of traditional medicine to Chinese medicine, excluding all other kinds of traditional medicine. Thus, the historical question of whether or not traditional medicine is a true medicine remains ultimately unanswered.