Karika 27

उभयात्मकमत्र मनः सङ्कल्पकमिन्द्रियं च साधर्म्यात्। गुणपरिणामविशेषान्नानात्वं बाह्यभेदाश्च ॥२७॥

Both the nature exists in the mind (to sense and to act), hence it is the Indriya of determination (saṅkalpakam indriyaṁ). Special effects of qualities (satwa, rajas, tamas) as per their dharma results in many fold variations, as well as differences in the external appearance.