YOU say theorems are useless. To whom? To such as apply them ill. For medicines for the eyes are not useless to those who apply them when and as they ought. Fomentations are not useless; poisers are not useless; but they are useless to some, and, on the contrary, useful to others. If you should ask me now, Are syllogisms useful? I answer, that they are useful; and, if you please, I will show you how. "Will they be of service to me, then?” — Why, did you ask, man, whether they would be useful to you, or in general? If anyone in a dysentery should ask me whether acids be useful, I answer. They are. "Are they useful for me, then?" — I say. No. First try to get the flux stopped, and the exulceration healed. Do you, too, first get your ulcers healed; your fluxes stopped. Quiet your mind, and bring it free from distraction to the school, and then you will know what is the force of reasoning.
EPICTETUS. DISCOURSES. Book ii. §21, ¶3.