What is the central idea of the passage?

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Every potent phenomenon is bound between the law of cause and effect. Though the cause is not visible, effect can be seen. An apple falls due to gravitation but we can’t just perceive it. So this force which is subtle, which is invisible can be felt only when we witness the gross object of this force i.e. the result. Every change that takes place is due to this hidden unseen subtle force. Our body too is an expression of this subtle force. Our body’s birth, growth, decay and death all revolve around this invisible concept. Even our rebirth or reincarnation depends on this subtle force. We gather many ideas, tendencies, desires which initiate a subtle body. When a person dies these feelings lie deep - untouched, undeciphered in the mind. These are stored as impressions in our mind but slowly they rise as physic waves and magnetize new desires. These desires lead to manufacture of a new body. The unfulfilled longing of “worldly pleasure”, the lust or cravings become the cause of rebirth. Till these retain themselves in the body they as a subtle force lead to hundreds of births. So, desires need to be accomplished if one wants to break free of the vicious circle of birth & death.