There are different kinds and different grades of living entities. Their standard of feeling happiness and miseries are also different grades. Animal. In the animal kingdom, they have no sense. One animal is being slaughtered; the other animal is seeing. Because he has no knowledge, the next turn is he is being turned . . . being slaughtered, but he is chewing some grass. He is happy. He is thinking that, "I am happy." Next moment it will be slaughtered, but he does not know. So these are all different grades of happiness.
But the highest standard of happiness is described here, sukham ātyantikaṁ yat tad buddhi-grāhyam atīndriyam. Buddhi-grāhyam atīndriyam. Buddhi means intelligence. One has to be intelligent. If you want to enjoy life, then you must be intelligent also. Just like the animals, they are not intelligent enough; therefore they cannot enjoy life as a human being can, standard.
So here, in the Bhagavad-gītā also, it is said that buddhi-grāhyam atīndriyam. Atīndriyam. Now, just take the example of a dead man. The senses, the hands, the nose, the sense organs and everything is there, but now he cannot enjoy. The dead body, it cannot enjoy. Why? This requires intelligence.