Much of our faith is invisible - the soul, Heaven, the power of the Sacraments. Our Catholic faith must be grounded in something more solid than what we feel and sense. Even if we don't actually experience God, we believe the testimony of those who saw the Risen Christ, who were willing to die testifying that He is alive. This gives us strength to believe them, and to believe all that the Apostles taught, even if we do not see it with our eyes!