If some rascal says that "I don't believe in the next life," that is his foolish thinking. He has to change his body. Nature's law is going on. You are not controller of the nature; you are controlled by nature. So if we entangle ourself with sinful activities, then next life means we get low-grade life. It is said in the Bhagavad-gītā:
- ūrdhvaṁ gacchanti sattva-sthā
- madhye tiṣṭhanti rājasāḥ
- jaghanya-guṇa-vṛtti-sthā
- adho gacchanti tāmasāḥ
- (BG 14.18)
Means those who are very pious, they are promoted to the higher planetary system. Those who are ordinary, they remain with the middle planetary system. And those who are very abominable, sinful, they go down planetary system or become lower than human being—animals, trees, birds, beasts, like that. So they have no sense. Their so-called scientific understanding has no, I mean to say, advancement of knowledge. They do not inquire even wherefrom these living entities are coming, the trees, birds, beasts, lower than human being; wherefrom they are coming they do not inquire.