Two words: bandhana, bondage, and mukti, liberation. So people in ignorance, dull-headed, mūḍha, they do not know what is mukti and what is bandhana, what is liberation and what is bondage. They do not to know. Just like animals. The animal, he does not know, the dog that, "I am bound up in this dog's body. This is bondage. This is not my life." He does not know. Similarly, a human being, if he does not know what is bondage and liberation, then he's animal. From animal life, this human life is evolved for understanding this: what is mukti and what is liberation.
So mukti and liberation, if you keep your consciousness materially affected . . . guṇeṣu saktam. Material world means the three qualities, tri-guṇa, guṇamayī. Kṛṣṇa says in the Bhagavad-gītā, guṇamayī, mama māyā. Mām eva ye prapadyante māyām etāṁ taranti te (BG 7.14). Tribhir guṇamayair bhāvaiḥ. We are being conducted in this material world by three guṇas: sattva-guṇa, rajo-guṇa, tamo-guṇa. Out of these three guṇas, the sattva-guṇa is the best: knowledge, the qualification of brāhmaṇa. Satyaṁ śamo damas titikṣā ārjavaṁ jñānaṁ vijñānam āstikyaṁ brahma-karma svabhāva-jam (BG 18.42). One who has developed sattva-guṇa, then the following qualification will be found in him: he'll be truthful and controlled of the mind, of the senses, satyaṁ śamo damas; titikṣā, tolerant; ārjava, simplicity; jñānam, jñānam, full knowledge; vijñānam, practical application of knowledge in life; āstikyam, āstikyam, to have full faith in the authority of the Vedas. That is called āstikyam. Āstikyam and nāstikyam.
Caitanya Mahāprabhu has explained what is nāstikyam and what is āstikyam. According to Vedic understanding, anyone who does not believe in the Vedas, he's called nāstika. Just like Buddha philosophy. Śrī Caitanya Mahāprabhu says, veda nā māniyā bauddha haila nāstika. Veda. Lord Buddha, he defied Vedic authority. His mission was different. He wanted to stop animal killing. Sadaya-hṛdaya darśita-paśu-ghātam. The Supreme Lord became so much afflicted by, terribly, people being attached to killing animals, as they are now doing also. So He was compassionate to stop animal killing in the so-called sacrifice. But in the Vedic sacrifices, in some cases, there is recommendation of animal killing. That animal killing does not mean killing the animal and eat. No. It was a test. An old animal was put into the sacrificial fire, and the animal would come in new body, young. That is animal . . . but to give, to test the Vedic mantra, whether it is properly chanted. Then the result will be that if you put one old body it will come new body. So such kind of brāhmaṇa is not available in this age, Kali-yuga, yājñika-brāhmaṇa. They, by mantras, they could, they would ignite fire. Fire was not required matches. By mantra. Simply by mantra, the old body of an animal will turn to be young.
But because the yājñika-brāhmaṇa cannot do that . . . there is no yajña. Not possible. Therefore this kind of yajñas are prohibited in this Kali-yuga. In the Kali-yuga the only one yajña is this saṅkīrtanam. Yajñaiḥ saṅkīrtana-prāyair yajanti hi su-medhasaḥ (SB 11.5.32). Those who are intelligent person, they know this kind of yajña will not be successful. Because people do not know, they cannot chant the mantras rightly, neither there is facility. So many things. Therefore in this age, dull age, the only concession is to perform saṅkīrtana-yajña. Yajñaiḥ saṅkīr . . . and yajña means to worship the Supreme Lord, Viṣṇu. Yajñaiḥ. Varṇāśramācāravatā puruṣeṇa paraḥ pumān viṣṇur ārādhyate (CC Madhya 8.58). Ārādhyate. Real purpose is to worship the Lord, Viṣṇu. Nānyat tat-toṣa-kāraṇam. Therefore performances of yajña is required.