It is also worth considering the argument that a belief in truth seems to be pre-programmed into us at a biological level. Although there is no logical reason to believe it, we all rely on the assumption that gravity will continue to operate, for example. Even though gravity was a force for the last 8,000-odd days of your life, 8,000 positives do not preclude a negative tomorrow. Nonetheless, before we even have the capacity to think about such abstract concepts we learn to walk and eat and sleep and a thousand other things that are 100% reliant on constant truth existing in our universe. In fact, learning itself relies upon this notion, and the capacity to learn and change is at the core of our existence.
It is somewhat pointless to suggest that all of these everyday assumptions should be questioned every single time they are relied upon - when you woke up each morning it would take you forever to get anything done. Furthermore, I do not believe the human brain even has that ability - if I throw something at your face without warning, your biology will kick in and try to protect you, no matter how much you believe on a philosophical level that it may or may not hurt.
What is interesting (at least to me) the the idea that we have the capacity be aware of the one big assumption, the big lie of existence that everyone swallows whole. It is the counterpoint to 'I think therefore I am' (ignoring Descartes' dubious proof of God for the moment) - basically, 'everything else I think is true is actually an assumption, but it's all I've got to work with.' It's like playing a game that may or may not be real. When you play chess, you know that it's just a bunch of pieces on a chessboard. Just because there is no real universal law forcing a knight to move in a certain way doesn't mean you can't still have fun playing with that constraint. When you play/live life, most people assume that the game is real, and hey, even if you disagree you can still have fun playing by the rules. If you figure out a way to get out of the game Matrix-style then please let me know (Lewis Carroll, anyone?). Alternatively, you could go and buy that god-awful board game the Game of Life and ignore all of this existensial rubbish.