As someone said earlier, there is only one truth. People may have different ideas about what that truth is. Assuming that anyone knows any aspect of the truth, does not mean that person knows the entire truth.
Also, knowledge of the truth does not prevent someone from distorting it to fit what they desire it to be. So the question is:
Can anyone know the truth?
My answer is of course yes. I live my life based on the fact that Jesus has been and will always be the truth. This doesn't prevent me or anyone else who believes this from adding our own twist to it (consciously or unconsciously).
Even if God tells me that my perception of the truth is wrong, I still have to make the decision to accept it.
I think the truth is that people are so self centered, that we would rather follow our own perception of the truth that makes us feel all warm and fuzzy inside. We think that our own personal experience is the only way to tell what the truth is.
I think that by looking at the totality of human experiences (psychological, physical, mental, emotional), one can find God's word (the bible) to be right on the mark. However, because we will always maintain some aspect of individual truth, there will always be those who don't come to a perception that is close enough to the truth to receive or accept God's grace and be saved.