Question: From an existential point of view, if one can only experience one’s own body at any time, isn’t one then the only truth one can “know”?
Answer: You are absolutely right. So much so that there is nothing outside of your “body”, whatever you consider “outside of yourself”, the inanimate, vegetative, animate and human part of Nature, they are simply the external projections of your self.
Now is this the “truth” you know? Yes whatever you perceive is your actual truth. But is it the “absolute truth”? No. In order to know the absolute truth you would need to acquire a selfless, objective perception. How? by using the “externally projected parts of you”, the “other Humans”, using their point of view, their desires to exit you present “observer point”, your present “self”.
Then by relocating yourself into those parts of you that seemingly exist outside of you, you finally become the real you, which is the selfless, objective, Human observer capable of viewing, understanding the absolute truth!
Entering The Force-Field 