The senses exist for simply catching the impressions of their respective objects. Doubt is the function of the Mind. The Understanding is for ascertainment. The soul is said to be only an inactive witness.
चक्षुरालोचनायैव संशयं कुरुते मनः। बुद्धिरध्यवसानाय साक्षी क्षेत्रज्ञ उच्यते।