For example . . . there are many examples. One of the example is that the Veda says that if you touch the stool of an animal, even your own stool . . . that is the system. In India still they are . . . not in the city, but in the villages you will see even ordinary man, he goes to pass stool in the field, and just after passing stool he will take bath just to purify himself, change his cloth. That is the śāstric injunction. But in one place it is said that the stool of the cow is pure.
Now if you argue that, "One place you say that the stool of an animal is impure, even your own stool if you touch you have to take bath, how is that, another animal's stool is pure?" This is superficially contradiction. But those who are following strictly the Vedic principles, they will accept that the stool of cow, or cow dung, is pure. Now, if you argue, "Why it is pure?" then you come to a modern chemical analysis, and you will find the cow dung is full of antiseptic properties. It has been examined in Calcutta by one doctor, Raj Mohan Bose. Therefore, the Vedic injunction is so perfect.
We ordinary human being, we have got four defects. First of all we commit mistake. Even big, big men, they commit mistake, because to err is human. Committing mistake is not a disqualification. As a human being, he is prone to commit mistake, everyone accepts: E and OE, errors and omission excepted. Similarly, a man is in illusion. Illusion means . . . just like the example of illusion is the mirage. In the desert or in very scorching heat, summer season, you can find before your car there is water, reflection. So this is called illusion. There is no water, but it appears there is vast mass of water. The animals are bewildered. They are thirsty; they go to the desert to take water. Where is water in the desert? This is called illusion.
So mistake, to commit mistake, to become illusioned, and through the propensity of cheating. Every man is imperfect, but he is talking just like perfect. That is called cheating. The so-called scientists, philosophers, they are theorizing, "It may be," "Perhaps." So what is this knowledge, "Perhaps," "It may be"? That is not knowledge. Say definitely. But nobody can say. They are blind. The doctor is giving medicine, but he is not definitely sure whether his patient will die or live. If you ask him whether the person is going to live, "Oh, that depends on God." Ultimately depends on God—although he is posing himself that authorized, he is giving scientific medicine . . . if you are giving scientific medicine, why you are not sure? This is called cheating. While he is not sure, still he says: "I am scientific man." This is one defect.