Caturvidhah savabhaavasca praakrto varngasta thaa I
utpaaditasca sangena suddhasca jnaaninaam smrtah II
In the Gita there is description of the four types of nature:-
(I) General Nature Pertaining to Prakrti:-
Germination of plants, trees and their growlh; birth, childhood, youth, old age of human beings, birds and beasts, strength and weakness of bodies and such other changes that are taking place in the world, are included in general nature pertaining to Prakriti.
This sort of nature instead of being faulty and harmful purifies beings. How can the change from childhood to youth and from youth to old age, as well as, from sickness to health* and from health to sickness be faulty? It rather purifies a person by enabling him to reap the fruit of his past virtuous and evil deeds. But in this nature of prakiti (nature change) a person acts with attachment and aversion against the ordinance of the scriptures in his own way which leads him to bondage.
This nature has been described in the Gita as follows:—“All actions are being performed by the modes of Prakriti” (3/27) “It is the Gunas (modes in the form of senses and mind etc) that move among the Gunas) as (objects of perception) (3/28); 14/23); “It is the senses that are moving among their objects” (5/8-9); “All actions are being performed in every way by Prakrti alone” (13/29). It means that a man should neither have his own way nor feel happy and sad while actions are performed by Prakriti.
* Sickness can be of two kinds- by fate and by unwholesome diet. The sickness caused by fate can not be cured of by taking medicines, it will linger unless the fruit of past deeds is fully reaped. But the disease caused by unwholesome diet is cured by medicines. Here (in general nature pertaining to Prakrti) disease caused by fate has been taken.