"You have asked me how one can know that Krishna is the Supreme Personality of Godhead? How do you know that the president is the supreme person in your state? You know this through the government organizations, the constitution papers, and by traditional knowledge. Similarly, to know Who is the Supreme Personality you have to take evidence from the Vedic authorities, great personalities, and the Spiritual Master. Otherwise, what is the use of accepting a Spiritual Master if you can not take His words? Your Spiritual Master says Krishna is the Supreme Personality of Godhead, Krishna says He is the Supreme Personality of Godhead, all the Vedic literature says that Krishna is the Supreme Personality of Godhead. All great authorities like Narada, Vyasadeva, Lord Chaitanya, Siddhanta Sarasvati, Bhaktivinode Thakur, Arjuna, and what to speak of the countless others say that Krishna is the Supreme Personality of Godhead. So to understand these authorities you have to follow in their footsteps. You cannot speculate upon Krishna, neither can you ever know Him by such speculations. You can simply use your judgement submissively; that is all, and this cannot be done in a challenging spirit. Lord Jesus Christ also said that the Kingdom of God is only for the humble and meek.
In regard to your next question, self realization means God realization, and God realization means self realization. Just like to see the sun means to see oneself, and to see oneself means to see the sun. Self realization depends completely upon God realization, or else it is not complete. One must know his relationship to the Absolute Truth to fully know his position. The mayavadi school simply discerns spirit from matter, but that is not Ultimate Knowledge. One should know the different manifestations of the spirit also. The highest manifestation of the spirit soul is the Supreme Personality of Godhead, Lord Krishna.
In this age the mind is so much agitated that it cannot be fixed up on the Supreme Objective. Real meditation means to fix up the mind on Krishna or on Krishna's Expansion, Lord Visnu. The modern so-called meditater has no information of Krishna or Visnu. They try to meditate on something void or impersonal which is simply troublesome. It is clearly stated in the Bhagavad-gita that those attached to the impersonal feature have their path to be very, very troublesome. Not only in this age when everything is troublesome, but it was so in former ages also, so what to speak of this age. Therefore, in this age, to fix up your ears upon the transcendental vibrations of Hare Krishna is the highest form of meditation, and the only one which will prove feasible for you. We may or may not condemn the impersonalists, but they are already condemned by Lord Krishna in the Bhagavad Gita."
(Srila Prabhupada Letter, January 22, 1969)
"Regarding your last question about the importance of chanting; this chanting process is the only way of attaining full Krishna Consciousness in this age of kali yuga. Lord Chaitanya stressed upon this point, and we may take it from His authority that no other method will prove to be successful in this matter."
(Srila Prabhupada Letter, January 23, 1969)
"Regarding your questions about the examinations to be given, the girls will also be able to take these. In Krishna Consciousness there is no distinction between girls and boys. The girls also may become preachers if they are able."
(Srila Prabhupada Letter, January 24, 1969)
"Regarding your question about why we dress the Deities in very opulent fashion and not as simple cowherds boy and girl, this is an intelligent question and the answer is that according to the regulative principles we cannot worship Radha-Krishna now. Radha-Krishna worship is meant for persons who have already developed spontaneous love of God. In the training period we are only worshiping Laksmi-Narayana. We worship Radha-Krishna because Laksmi-Narayana is there also, but actually we do not worship Radha-Krishna with our present Deity ceremonies; we are worshiping Laksmi-Narayana. Narayana is there when Krishna is there, but actually we do not worship Radha-Krishna in Their Original Form. This is why we should worship Radha-Krishna in Their Laksmi-Narayana feature with all respect and reverence. If we deviate from this standard then we shall be prakrta sahajiya, or a person who takes things very cheap. We worship Laksmi-Narayana, and because Radha-Krishna includes Laksmi-Narayana, there is no necessity of installing a Laksmi-Narayana Deity. It is just like a king who is engaged in administering justice. Actually that business belongs to the justice department. But what is that justice department? It is all part of the kings energy, and the king also has the power to execute this function.
Regarding the blood and puss from the sky during the battle between Varaha and Hiranyaksa, you should know that if Krishna desires blood, puss, fire, or whatever He desires may fall down from the sky."
(Srila Prabhupada Letter, January 24, 1969)
"Regarding your questions, the so-called love which goes on in the material world is simply a perverted form of dasya rasa. Everything in this world is a perverted form of rasa. Just like Yasoda is loving Krishna as her Son. So this is vatsalya rasa, parental love. When Krishna is separate from Yasoda, she cried for whole life and thus became blind. In this world there is not a single instance where a mother has suffered so much in separation from her son. Therefore, it is perverted reflection of the real love. Regarding your second question, the other names of Krishna which you have mentioned, such as Gopala and Govinda are as powerful as the name Krishna."
(Srila Prabhupada Letter, January 25, 1969)
"Regarding your question, maya comes from Krishna. Everything comes from Krishna, but when something is found in Krishna it is just as good as anything can be. Just like Krishna has the stealing propensity. As such He is called the Butter Thief, and he is worshiped as the Butter Thief. He is worshiped by His devotees all over the world with love and affection, while the same propensities in us would result in our being handed over to the police. That is the difference between Krishna and ourselves. He being Absolute, everything in Him is also Absolute. In the relative prospective it is very difficult to understand what is the Absolute. From the material point of view, one cannot understand that one plus one equals one, and one minus one equals one. It requires a little time to understand this axiomatic truth. But in time such truths will become revealed to you without any mental speculation."
(Srila Prabhupada Letter, February 1, 1969)
"Regarding your question about Subhadra and Durga, they are not at all the same. Durga's other name is Bhadra, not Subhadra, and Durga's activities are within the material world. Subhadra does not work as Durga. Subhadra is internal energy, and Durga is external energy. As energy, they have a relationship as much as we are energies of Krishna, but the energies are working in different capacities. Although originally the energy is one, by their expansion, the accents of the energies are different, and as we are not impersonalists, this variegatedness of actions are essential for the Supreme Personality of Godhead, as much as the government is one but there are multi-departments for management of the government. The education department and the criminal department are all departments of the government. The government is connected with all parts and departments, but the education activities are different from the criminal activities. This is the philosophy of inconceivably simultaneously one and different manifestations of the Absolute Truth."
(Srila Prabhupada Letter, February 9, 1969)
"Regarding utilizing intelligence in devotional service, intelligence should be confirmed by the Spiritual Master. Therefore we accept the Spiritual Master for guidance. You should not depend on your own intelligence. Just like a child requires a parent to tell him the correct thing to do, similarly, a strict disciple should always use his intelligence in conformity with the instructions of the Spiritual Master.
Regarding your dealings with impersonalists, any one who teaches of the impersonal nature should be avoided. If we hear them, it will hamper our progress. That will be the result—no progress. Therefore, rigidly we will try to avoid the impersonal teachings. Generally, it only produces bad effects.
As for your question about the ecstasy of chanting and working for Krishna, the ecstasy which is automatically manifest is very welcome, but we should not try to come to the ecstatic status by any artificial practice. You should give more stress on the importance of chanting. Working for Krishna is not different from chanting, but such work would be done under the direction of the Spiritual Master."
(Srila Prabhupada Letter, February 13, 1969)