It is commonly held that the search for truth is successful in proportion to the readiness of truth searchers to put aside their original beliefs and to accept whatever belief will appear to be proven. This view is taken for granted by both philosophers and non-philosophers. I call it mere epistemology. In this dissertation, I first argue that there are various problems with mere epistemology. First, it falls into a self-referential contradiction. Second, it does not explain the inconclusiveness that— especially in religious matters—besets debates in proportion to the commitment of debaters to their original beliefs. I then focus on religious debates and show that Christian believers offer, more or less implicitly, significant suggestions regarding the problem of inconclusiveness. They seem expected to commit themselves to God and to related beliefs no matter how convincing the evidence contradicting such beliefs may appear to be. This, however, causes not only inconclusiveness but also various beneficial effects on the intellectual activity; furthermore, it determines in some measure unbelievers also. In short, believers and unbelievers can commit themselves to God and the good, respectively, which means that they assume good habits in any activity they take. I call spiritual turn this assumption of good habits in the intellectual enterprise. It is a turn from mere epistemology, whose supporters first commit themselves to the search for truth—they maintain that every commitment must firstly be individuated epistemically. Unlike them, those who take the spiritual turn first commit themselves to God and/or the good, based on the conviction that this causes human flourishing and consequently perfects any human activity, the intellectual one included.