Is it okay to have a character who only thinks, and doesn't talk?

I'm in the middle of writing something and I realized that there is no reason for my character to talk at all. He's alone. Is it okay if he's silent?

Why wouldn't it be OK?

If the story calls for it, then it's fine.

You know, there's actually a word we use for people who are physically unable to talk. It's called being mute.

Snoopy seems popular.

He's not physically unable to talk, there just isn't anyone to talk to.

There really isn't a reason for him to vocalize his thoughts anyway if this is a written work. It's not like it's a film and you need sound.

Then don't have him talk.

Okay, I've never done something like this before and I didn't know if it would be stupid. I'm trying to make it scarier by have=ing him be alone.

there is no issue.

Ever read One Flew Over The Cuckoos Nest?

If the character doesn't have to talk, then there's no reason to include it.

Horror in particular benefits from a lack of dialogue - take H.P. Lovecraft, for example.

I wrote a super-long ff with a mute main character (no writing, no ASL til very near the end). It's a challenge, but it's do-able.