The fact that fire will burn is pre-destined (the cause and effect). Whether to put finger in fire or not is the free will that I can exercise. Vidhi is that fire will char the flesh, my free will is whether to get my finger charred or not. Whether I put my finger or not will be based on my previous thoughts and actions (Karma). Karma is action which originates from thoughts. No action can be performed without a thought. So to change karma one has to change the thoughts. In Kali Yuga the wandering or outward seeking mind would be to the extreme and so too much bad actions results.