Knowing this first, that no prophecy of the scripture is of any private interpretation.
This passage is commonly quoted when a person wants to convey the idea that the Bible cannot be privately or individually interpreted – that each reader cannot say the Bible means something different for each individual. While I agree that the Bible must speak for itself and that the Bible does not mean something different for each individual, this verse does not support that. Let’s look at the surrounding passages:
2 Peter 1:19-21 (KJV) We have also a more sure word of prophecy; whereunto ye do well that ye take heed, as unto a light that shineth in a dark place, until the day dawn, and the day star arise in your hearts: 20 Knowing this first, that no prophecy of the scripture is of any private interpretation. 21 For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Ghost.
As you can see, the passage is talking about the origin of scripture – that the scriptures did not come about from the private interpretation of events as viewed by the penman. The scriptures came about as God moved holy men by the Holy Spirit and not as the result of the penman’s will. This passage does not address how a person can or cannot reach a conclusion as to the meaning of the scriptures.