So, na satyaṁ teṣu vidyate. The demonic people, they do not have the truth. Only a false theory, the Darwin's theory. We have commented upon Darwin's theory also in our book Scientific Basis of Kṛṣṇa Consciousness. Dr. Svarūpa Dāmodara Brahmacārī, he has written a small booklet. He has criticized Darwin very strongly, that he is a speculator. A speculator cannot give you truth. That is not possible. By speculation you cannot say, "Two plus two equal to five." That is not science. "Two plus two equal to four," that is everywhere. And if you speculate, "No, two plus two equal to five," or "Two plus two equal to three," that is not science. So scientific basis means it should be fact, not speculation. Mano-dharma, mano-dharma means speculation.
Therefore śāstra says, harāv abhaktasya kuto mahad-guṇā mano-rathenāsati dhāvato bahiḥ (SB 5.18.12). Harāv abhaktasya, one who is not a divine nature or devotee of the Lord, he has no qualification. "Oh, he's M.A., Ph.D." No, he has no qualification. "Why?" Now, mano-rathena, he is simply speculating. He has no truth. How by speculation . . .? Every one of us, we are imperfect. We are very much proud of our eyes: "Can you show me?" What qualification your eyes have got that you can see? He does not think that, that "I have no qualification; still, I want to see." These eyes, oh, they are dependent on so many condition. Now there is electricity, you can see. As soon as there is electricity off, you cannot see. Then what is the value of your eyes? You cannot see what is going on beyond this wall.
So don't believe your so-called senses as the source of knowledge. No. The source of knowledge should be by hearing. That is called śruti. Therefore Vedas name is śruti. Śruti-pramāṇa, śruti-pramāṇa. Just like a child or a boy wants to know who is his father. So what is the evidence? That evidence is śruti, hearing, from the mother. Mother says, "He is your father." So he hears; he does not see how he became his father. Because before his body was constructed the father was there, now how could he see? So by seeing, you cannot ascertain who is your father. You have to hear from the authority. The mother is the authority. Therefore śruti-pramāṇa: the evidence is hearing; not by seeing. Seeing . . . our imperfect eyes . . . there are so many obstacles. So similarly, by direct perception you cannot have the truth.