Chanting Only.
Question: Is it possible to go back to the spiritual world just chanting the Mahamantra without accepting diksa from a spiritual master?
Romapada Swami: As described in Caitanya Caritamrita, to chant the holy name of the Lord one need not depend upon other paraphernalia or practices, for one can immediately get all the desired results of linking with the Supreme Personality of Godhead. It may therefore be questioned why there is a necessity for initiation or further spiritual activities in devotional service for one who engages in the chanting of the holy name of the Lord. The answer is that although it is correct that one who fully engages in chanting the holy name need not depend upon the process of initiation, generally a devotee is addicted to many abominable material habits due to material contamination from his previous life due to which one is not able to chant the Holy Name without offenses.
Unless one is on the platform of Sukadeva Goswami, one requires diksa. Even in Sukadeva’s case, although fully realized in Brahman with no attraction for anything material [SB 1.7.9], he took the position of sisya to learn SB from Vyasadeva. See SB 2.1.8 “At the end of the Dvapara-yuga, I studied this great supplement of Vedic literature named Srimad-Bhagavatam, which is equal to all the Vedas, from my father, Srila Dvaipayana Vyasadeva.”
Kripa-siddhi is also possible.
Both of these are exceptions to the rule.
In the purport to the verse where Arjuna accepts Krishna as His spiritual master (Bg. 2.7), Srila Prabhupada describes how in this material world, there is perplexity in every step and this behooves one to approach a spiritual master. Arjuna was in total despair and confusion about his duty and what is best for him.
Similarly, by arrangement, the conditioned soul repeatedly finds himself/herself in the midst of perplexities, bewilderment and despondency. Srila Prabhupada also explains the culmination of all these repeated fleeting problems are the insurmountable problems of repeated birth and death.
One, therefore, needs the guidance of a Spiritual Master from whom one can inquire about the ultimate solution to all these problems, and to inquire into the subject of the Absolute Truth.
Specific to diksa, the initiation ceremony, far from being merely a colorful ritual, is a necessity for genuine spiritual life. Although everyone, even if not initiated, is encouraged to chant Hare Krsna and will receive spiritual benefit if he does so, unless one is initiated by a genuine spiritual master he will not receive the spiritual strength to remain steady in chanting Hare Krsna Mahamantra and following spiritual principles, and after some time he may slide down again to material consciousness. The non-initiate is sometimes compared to a student who is allowed to sit in on a professor’s class but who has not officially registered for the course. Although such a student may benefit by auditing the class, he must formally join the class if he wishes to receive college credit. Similarly, only when one is initiated does he become eligible for the full benefits of Krsna consciousness, for then his link to Krsna is established, through his own spiritual master and all the great spiritual masters of the past. Then, by implicit faith in his own spiritual master and in Lord Krsna, all the truths of the Vedic literature are revealed to him. This is the path for the serious candidate on the path of spiritual perfection.