This sermon discusses three crosses: 1) The cross of Calvary, where Jesus sacrificed himself to show humanity how to live selflessly. 2) The cross of matter, referring to the eternal sacrifice where life limits itself by taking form in the material world to nourish creation. 3) The cross of our own hearts, where we can experience crucifixion by letting go of selfishness and resurrection by living selflessly for others through following Christ's example. All three crosses represent the same principle of selfless love through sacrifice that sustains both humanity and the cosmos.