Devotee: "Now in the Fourth Chapter the Lord tells Arjuna that this yoga system of the Bhagavad-gītā was first spoken to the sun-god. The Blessed Lord said, 'I instructed this imperishable science, imperishable science of yoga to the sun-god, Vivasvān, and Vivasvān instructed it to Manu, the father of mankind, and Manu in turn instructed it to Ikṣvāku. This supreme science was thus received through the chain of disciplic succession and the saintly kings understood it in that way. But in the course of time the succession was broken and therefore the science as it is appears to be lost.' "
Prabhupāda: That is the instruction in the Bhagavad-gītā, that this science of Bhagavad-gītā has to be accepted by disciplic succession. That is the way of accepting any scientific thing. Just like even in material science, suppose if you have to become medical practitioner or a lawyer. So you have to study the law books by the previous lawyers, by the judgments of the courts. One who has studied the previous records of legal implications, he is best lawyer. Similarly a medical practicer, practitioner, who has studied the previous books and knowledge and experience, he is called experienced physician.