Q. Why do we assume that Krishna is the only Lord while infact Krishna is also one of the incarnations of Vishnu?
Krishna has also birth. If we think that in Bhagavadgita, Krishna is recommended as the Lord, then in the same way in Shiv Puran, Shiv is the Lord and in Vishnu Puran, Vishnu is the God. Then, how to know that Krishna is the only Lord?
A. Our accepting Krishna as God is not an assumption or a fanatical declaration. It is based on authoritative scriptures and the statements of great acaryas coming in disciplic succession.
The entire Vedic literature consisting of several Upanishads and Puranas are meant to address specific groups of people according to their consciousness levels. All of them do not belong to the same group. Primarily, they are classified into three: some of them are meant for people in the mode of goodness, some for people in the mode of passion, and others for those in the mode of ignorance. So, when there are differences of opinion among Puranas regarding the identity of God, it is not a contradiction; they are speaking with reference to a particular context and a group of people.
For Example: In preliminary arithmetic, we are taught that two minus five does not exist, whereas in advanced mathematics, this is a perfectly valid expression. This is not to say that mathematicians are contradicting each other, but actually the concepts are revealed according to the capacity of the student. Similarly, the Vedas speak of many subjects some of which may appear contradictory, but they are meant for different levels of readers according to the material modes they are situated in.
Having said this, the risk of someone misinterpreting and twisting the meaning of the Vedas still remains nevertheless. Therefore, we need the guidance of the acaryas, spiritual teachers, who are connected to God in an unbroken disciplic succession. When we receive knowledge from them, we can be rest assured that there is no error.
The Bhagavad-gita is considered the essence of all Upanishads and the Srimad-Bhagavatam is the essence of all Puranas. Both these scriptures emphatically declare that Krishna is the Supreme Personality of Godhead. And these statements are confirmed by all the great spiritual teachers.
Regarding Vishnu and Krishna: Essentially there is no difference between the two; they are just two different forms. Vishnu is like God in office (Vaikuntha), whereas Krishna is God at home (Vrindavan). Krishna’s pastimes are more intimate and sweet, whereas Vishnu’s dealings are mainly based on awe and reverence.
Scriptures like Brahma-samhita give the example of a candle from which many other identical candles are lit. Although each candle has the same power as the original, the first candle still remains original, being the source of light for all candles. Krishna is like the original candle while all the other incarnations are like the other candles. Although both Vishnu and Krishna have the same potential, Krishna still remains the original person.
Generally all incarnations come through Vishnu who is in charge of maintaining law and order within the universe. However, Krishna is not just another incarnation; He is the original Supreme Personality of Godhead, the source of all incarnations including Vishnu. When He appears (only once in a kalpa or a day of Lord Brahma), He continues to maintain the same protocol of coming through Vishnu. That’s the reason why people incorrectly call Him an incarnation of Vishnu.