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To perceive directly : have direct cognition of    
For the which cause I also suffer these things: nevertheless I am not ashamed: for I know whom I have believed, and am persuaded that he is able to keep that which I have committed unto him against that day.
He was persecuted by fellow Christians who did not understand Grace, holding on to legalism.     He was persecuted by those protecting their pagan religions.     He was able to endure this because he really knew in whom he had believed.

A personal Relationship with Christ Jesus implies that you don`t just Believe on Him but that you Know Him.   

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