You would him/her Gullible.
A person who believes in aliens is often referred to as an "alien enthusiast" or someone who is "believes in extraterrestrial life."
Gullible.
Religious.
A creationist.
I would call him a god, or at least someone who believes he is a god.
A person who believes that war is wrong is called a "pacifist".
One who believes that everything is predistined -FATALIST
She believes in God.
Lonely!
An opinion
psycho
A person who believes in science is often referred to as a scientist or a rationalist.