Before the tragic incident involving his daughter, Callaghan was apparently a good-hearted, loving man, bent on changing the world for the better through the wonders of science and technology. He presented himself as a humble figure, with the wisdom to guide young minds down a bright path, in addition to serving as a father figure to his students; specifically towards Tadashi. Above all, his only true love and concern was Abigail, referring to her as his "everything", and valuing her above all others