On the afternoon of October 12, 1990, my twin brother Thomas entered the Three Rivers, Connecticut Public Library, retreated to one of the rear study carrels, and prayed to God the sacrifice he was about to commit would be deemed acceptable. (1.1)
The very first line of the novel sets us up for some religious turmoil. Unfortunately, we never get inside Thomas's head, because Dominick is the narrator. Could Thomas actually be hearing the voice of God? Would God want him to cut off his own hand?
If Thomas hadn't latched onto that Bible voodoo—that "if your right hand sinneth then cut it off" crap—then none of this would have happened. (3.31)
Dominick criticizes Thomas for taking the Bibleliterally. How does a person know which parts of the Bible are meant to be taken literally, and which parts are more symbolic?
[Ma] taps her finger against Jesus' chest. When she moves the painting, you can see Jesus' heart on fire. (5.26)
Thomas learns a lot of his religious behavior from his mother, a person who finds this moving painting with Jesus' heart on fire to be beautiful and inspiring instead of, say, creepy and weird.
Ma had prayed to Saint Anne for good weather and saw this sudden clearing as a small miracle, a further sign of what everybody knew already: that Heaven was on our side, was against the godless Communists who wanted to conquer the world and blow America to smithereens. (2.50)
What's the difference between Ma believing this and Thomas believing that he, too, is doing God's work?
Once people heard what he had to say, [Thomas] told me, he would find his flock. His ministry. And he probably would, too, knowing how many lunatics were out there. (7.53)
We'd liked to have seen an alternate version of I Know This Much is True with Thomas as a cult leader. What type of people would look up to him?
Either God was so hateful that He'd singled us out for this (Dessa's theory) or that there was no God (mine). Life didn't have to make sense. That was the big joke. (14.18)
Dominick would like to position himself as Mr. Tough Atheist, as though that's the antithesis of Thomas's religious mania, but the truth is that Dominick is mad at God… and you can't be mad at something you don't believe exists.
When I was six, the Virgin Mary herself confirmed the suspicions of the village women that, amongst the children of Giuliana, I was speciale! [sic] (31.12)
There are lots of similarities between Domenico and Thomas, but the main difference is that people actually believe Domenico in 1900. If it were 1990, they'd try to institutionalize him.
As I have said before, a modern man such as Domenico Tempesta leaves superstition to foolish old women. (37.34)
Yes, he'll leave "superstition" to foolish old women, but he'll still believe that the Virgin Mary https://www.shmoop.com/matthew-gospel/mary.html chose him as a special one as a child. What's the difference between superstition and religion?
Thomas asked me if I believed in God. […]
"I wish I did." (40.187, 40.189)
Dominick probably wishes he believed in God because that would give his life a grounding force. By this point in the novel, Dominick doesn't know anything is true; he's completely lost.
"He was religious," Ray said.
"He was crazy," I snapped back. (42.4-42.5)
Whether Thomas was crazy or not, his lived his life by some version of Christianity, so it's important for Ray and Dominick to find some sort of compromise when it comes to religion for Thomas's funeral.