28 The search for truth, of course, is not always so transparent nor does it always produce such results. The natural limitation of reason and the inconstancy of the heart often obscure and distort a person's search. Truth can also drown in a welter of other concerns. People can even run from the truth as soon as they glimpse it because they are afraid of its demands. Yet, for all that they may evade it, the truth still influences life. Life in fact can never be grounded upon doubt, uncertainty or deceit; such an existence would be threatened constantly by fear and anxiety. One may define the human being, therefore, as the one who seeks the truth .
Source: Fides et Ratio (Vatican.va)