Dr. Makoto Kondo, a radiologist at Keio University, has suggested that one should not fight against cancer. His arguable claims are that (1) cancer screening is ineffective and that (2) cancer is divided into two categories: true cancer and pseudo-cancer ("gan-modoki" in Japanese). The former has a strong potential to be invasive and has already reached the invasive state on detection by screening. The latter is noninvasive and therefore the affected patients need not undergo medical treatment unless they exhibit some symptoms. Kondo highlights the evidence provided by medicine and informs us of how poor its basis is. It should be noted that he reached this conclusion through in-depth reflection on findings regarding cancer, without submitting to the opinions of the authorities. From the perspective of philosophy of medicine, we may state that his attitude is that of a philosopher. However, he also discourages patients who believe that cancer screening and treatment are effective. On the other hand, Dr. Toru Abo, an immunologist and a professor at Niigata University, has developed a theory regarding the close relationship between the autonomic nervous system and the immune system, and maintains that cancer can be cured by activation of the latter. In contrast to the claims of Kondo, many of Abo's claims lack medical evidence, but he offers hope to patients. Kondo's theory is based on positivism, and he does not raise the hope of patients. Kondo's position is very effective in revealing the insubstantial basis of medical science, but he confronts patients with nihilism, while Abo offers hope without considering the fact humans are mortal. Based on the opinions of these two doctors, we can reflect on the limits of application of positivism in medicine and the importance of the optimism that patients display and their individual initiative.