The mind has doubt or its essence. The understanding discriminates and produces certainty. The Soul becomes known as Jiva or individual soul when invested with body through the consequences of acts.
व्यवसायात्मिका बुद्धिर्मनो व्याकरणात्मकम्। कर्मानुमानाद् विज्ञेयः स जीवः क्षेत्रसंज्ञकः॥