Now Thomas (also known as Didymus), one of the Twelve, was not with the disciples when Jesus came. So the other disciples told him, “We have seen the Lord!” But he said to them, “Unless I see the nail marks in his hands and put my finger where the nails were, and put my hand into his side, I will not believe.” (John 20: 24,25)
One important thing St. Thomas shows us is theological arguments and the testimony of others are poor substitutes for a direct personal encounter with the truth. The fundamental purpose of human life is to enter into personal relationship with the living center of consciousness who holds all things in being. Belief without personal experience is like eating the menu instead of the meal. A purely intellectual enterprise is not belief. Knowing and loving are believing.