Throughout history philosophers have theorized about cognitive bias and its role in mass indoctrination and often describe it as an evil that captivates the minds of the masses, which prevents them from accessing the coveted realm of freethinking. However, they disagree over whether one should attempt to educate the masses or to distance oneself from them. In this class, we will engage with some philosophical views on cognitive bias and discuss the various approaches philosophers adopted for dealing with it in modern and ancient times.