Acharya Prashant explains that while an external teacher can be helpful, the ultimate and final teacher resides within oneself. He emphasizes that even if a physical teacher is present, their words will remain ineffective unless the listener's own heart and inner self grant permission to listen and understand. This inner capacity for awareness and comprehension is what he identifies as the soul or the true inner guide. Without this internal alignment and surrender to the truth, the mind remains distracted, and the external teacher's efforts go to waste.