Giles Corey is a strong old man who has recently converted to Christianity. He's likeable but is not too bright. His biggest bumble in the play is when he brings up the fact that his wife reads strange books. To Giles, any book is strange, and the idea of a woman wanting to read blows his mind. His mention of this fact leads to an accusation that his wife is a witch.
Giles feels terrible about this. He knows his wife is innocent and recognizes that his actions have led to her incarceration and impending death.
Giles Corey in the Essays