We cannot assume that what we believe is true unless we actually have a pure source of truth. What is the origin of truth and can it be manipulated by perceptions? Of course it can. How will that undermine everything you believe if what you thought was true is not based on reality but that perception? We feel comfortable if our beliefs are based on what think is firm ground. But what if you were told that your thinking is firmly based on foundation of sand?
Where is the pure source of truth?