Prot: You know what I've learned about your planet? There's enough life on Earth to fill 50 planets. Plants, animals, people, fungi, viruses, all jostling to find their place, bouncing off each other, feeding off each other. Connected.
Dr. Mark Powell: You don't have that kind of connection on K-PAX?
Prot: Nobody wants, nobody needs. On K-PAX, when I'm gone, nobody misses me. There would be no reason to. And yet I sense that when I leave here... I will be missed. Yes. Strange feeling.
Prot: Do I smell apple pie?
Prot: Doctor... patient... curious distinction.
Dr. Mark Powell: Oh, 6:15 was late. Didn't leave the station till 6:30. Should have caught the nearest beam of light.
Dr. Mark Powell: Have a seat.
Prot: "Have a seat." What a curious expression.
Dr. Mark Powell: How do you know right from wrong?
Prot: Every being in the universe knows right from wrong, Mark.
Prot: I shall miss Earth, it has great potential.
Prot: Doctor. Doctor. Doctor. Doctor. How many doctors are there on this planet?
Prot: I will admit the possibility that I am Robert Porter, if you will admit the possibility that I am from K-PAX. Now if you'll excuse me, I have a beam of light to catch.
Dr. Mark Powell: What would you say if I told you I think you're as human as I am?
Prot: I would say you're in need of a thorazine drip, Doctor.
Dr. Mark Powell: 26:16 Let me tell you something, Mark. You humans. Most of you subscribe to this policy of an eye for an eye. A life for a life, which is known throughout the universe for its stupidity. Even your Buddha and your Christ had quite a different vision. But nobody has paid much attention to them, not even the Buddhists or the Christians. Sometimes, it's hard to imagine how you've made it this far.
Howie: You never gave me my third task. What's my third task?
Prot: To stay here, and be prepared for anything.
Prot: I travel light.
Ernie: Dying is something you have no control over. Why waste your life being afraid of it?
Answer: He rejects it for two main reasons. First, each of the items you mention have possible, even if unlikely, explanations. Some people have strange or no reaction to certain drugs (for example I have almost no response to any painkillers). People who have had their corneas replaced with artificial lens can see near ultraviolet (though nowhere near 300-400 angstroms). The sheriff described Porter as being very bright, and he was in to astronomy, so while a great stretch, not impossible he somehow formulated the information he presented. The second reason, building upon these, is Occam's razor. As a person in the sciences, Dr. Powell is driven to believe things have a reasonable explanation, even if we don't currently know what it is, and thinking Prot is just a bright and unusual human is a more reasonable belief to him than believing Prot is an alien possessing a human's body.
jimba
Just remarking, there's no comparison of painkillers and psychiatric drugs. Thorazine and Haloperidol (Haldol) are both powerful anti-psychotic drugs with numerous side effects. Prot is immune to Thorazine and Haloperidol (as well as alcohol), which is more than extraordinary, it's otherworldly.
Charles Austin Miller