18.41 ब्राह्मणक्षत्रियविशाम् of Brahmanas, Kshatriyas and Vaisyas, शूद्राणाम् of Sudras, च as also, परंतप O Parantapa, कर्माणि duties, प्रविभक्तानि are distributed, स्वभावप्रभवैः born of their own nature, गुणैः by alities.Commentary: Brahmanas, Kshatriyas and Vaisyas are alified to practise the Vedic rites. The members of the fourth class, O Arjuna, have no claim to these rites, for their profession is to serve the members of the first three. They are not allowed to study the Vedas or perform Yajnas. There is organisation of mankind into the four castes and each mans life is divided into four stages, according to the nature of the Gunas and the degree of the growth or evolution. I will now explain the specific duties of these castes according to the alities by means of which, freeing themselves from the grip of birth and death, they can attain Selfrealisation or knowledge of the Self. Passion (Rajas) slightly mingled with Tamas causes the growth of the merchant caste (the Vaisya). Rajas mixed with Tamas is the cause of the appearance of the Sudra.The one human race has been divided into four castes based upon the three alities. The duties are allotted to each according to the alities born of Nature.Nature (Svabhava) is Isvaras Prakriti (Maya) constituted of the three alities -- Sattva, Rajas and Tamas.The Brahmanas nature is Sattva. So he is serene. The nature of the Kshatriya is Rajas and Sattva. Sattva in his case is subordinate to Rajas. Rajas predominates. Therefore he possesses lordliness. The nature of the Vaisya is Rajas and Tamas. Tamas is subordinate to Rajas. So he does various sorts of activities or business to earn money. The nature of the Sudra is Tamas, with subordinate Rajas. He is dull.Karma is action arising from and fashioned by past thoughts and desires. The Gunas cannot manifest themselves without a cause. Nature is the tendency, Samskara or Vasana in living beings. This is acired by them in the past births. This manifests itself in the present birth and produces its effects. This nature is the source of the Gunas. Every man or woman is born with his or her own Svabhava (nature). The Gunas operate according to the respective natural tendencies of man which impel him to perform his own duties as their natural effects. The duties are allottted to the four classes or castes in accordance with the Gunas of individuals. (Cf.IV.13)