In the play Magic, what does the conjurer mean when he tells Reverend Smith that he wants the Reverend to be martyred?

In this play, the conjurer, who usually does his magic act through trickery and sleight of hand, actually performs magic. However, nobody who knows him will believe him, because all they believe in is the rational world of science. They think the conjurer is lying when he says he performed real magic, because that is outside of the realm of their experience. Therefore, the conjurer says to the Reverend Smith:

I want you to be martyred. I want you to bear witness to your own creed. I say these things are supernatural. I say this was done by a spirit. The Doctor does not believe me. He is an agnostic; and he knows everything. The Duke does not believe me; he cannot believe anything so plain as a miracle. But what the devil are you for, if you don't believe in a miracle? What does your coat mean, if it doesn't mean that there is such a thing as the supernatural? What does your cursed collar mean if it doesn't mean that there is such a thing as a spirit? [Exasperated.]

The conjurer wants Smith to be martyred, to suffer and die for his faith, in the hopes that it will help convince rationalist, agnostic people like the doctor and the Duke that the spiritual realm is real. The conjurer also wants to know for his own sake that the reverend is a true Christian who believes the teaching of his church. The conjurer believes that, through the sacrifice of becoming a martyr, Smith would demonstrate that he really does believe in Christian teachings.