Was this image impressed upon the cloth by the heat or light of new life? No laboratory will ever tell us, nor can any scientists give such questions a scientific answer. The questions are important, not because we can ever hope to answer them with human knowledge, but because they lead us to the ultimate question about Jesus: does his story make sense?
“The bread that I shall give is my flesh for the life of the world,” said the Johannine Jesus. We do not have to adopt the theology of substitution – the theory that God required a spotless victim to make up for human sin – to make sense of the crucifixion … But Jesus’ suffering body is surely his ultimate gift, for it is his final act of sympathy with us…
When they come to Jesus, he seems already dead, so they do not break the bones of this Pascal Lamb without flaw. Just to be sure, however, “one of the soldiers pierced his side with a lance, and at once blood and water flowed out” – witnessed, writes John, “by the one who saw it,” the Beloved Disciple. This blood and water, the last drops of Jesus’ wracked body, seem to have flowed copiously, if we accept the visual testimony of that strange Fifth Gospel, the shroud, which may have been a treasure of the church of the Beloved Disciple, the same church that treasured the evolving Fourth Gospel.
— Thomas Cahill
Desire of the Everlasting Hills:
The World Before and After Jesus: