Spiritual nature, parā prakṛti. The material nature is aparā prakṛti, and we living entities, we are trying to enjoy this prakṛti. Therefore sometimes the living entity, either man or woman, he is described as puruṣa. Puruṣa means the one who keeps the feeling of becoming enjoyer. That is puruṣa. So this material world is prakṛti and puruṣa. It is said in the Śrīmad-Bhāgavatam in the instruction of Ṛṣabhadeva, puṁsaṁ striyā mithunī-bhāvam etat (SB 5.5.8). The whole basic principle of materialistic civilization is the attachment between man and woman. Puṁsaṁ striyā mithunī-bhāva. Mithunī-bhāvam is sex. And tayor mitho hṛdaya-granthim āhuḥ: on account of this sex relationship, the man or woman is bound up. Hṛdaya-granthi. Granthi means knot, and hṛdaya means heart. So the man is thinking of the woman, and the woman is thinking of man. Hṛdaya granthim āhuḥ. Then we require material possession: ataḥ gṛha-kṣetra-sutāpta-vittair janasya moho 'yam ahaṁ mameti (SB 5.5.8). This is our material, conditional life.
So this man, although he was being trained up as a brāhmaṇa, his attention was diverted all of a sudden by seeing one śūdra and śūdrāṇī embracing, kissing, talking. So that became his meditation. Instead of meditating on Viṣṇu, he began to meditate on that śūdrani. Svayam eva toṣayām āsa. In the first verse, tan-nimitta-smara vyāja-graha-grasto vicetasaḥ (SB 6.1.63). He became mad, vicetasa, bewildered, as if haunted by ghost. Tām eva manasā dhyāyan. Always meditating, "How shall I get that woman? How shall I please that woman so that she may satisfy my lusty desires?"