I'm gonna try to be as brief as possible. I play guitar in a 3 piece indie/garage rock band. The main problem is that I want there to be another guitarist to play lead guitar so I can focus on rhythm (I sing in the band too), but the bassist (who also sings) doesn't want to add any new members. The drummer (who agrees with me) and I have asked him why he doesn't want another guitarist but he never says exactly why, only that he "won't be happy with the band anymore." We told him that we can try some people out and see how it goes and that we won't add anyone if it doesn't feel right but he doesn't even want to do that. Also, we've never had a second guitarist, so it's not like he's speaking from a bad experience that we may have had.

Kicking him out is not an option, he's a great songwriter, musician and friend and I'm not kicking him out of the band over this. I just want some advice on how I could convince him to at least let us try out some other guitarists with no guarantee that we will even add anyone. I also should add that even though the drummer and I both think we should add a second guitarist, we aren't the type of band to say "majority wins," we want everyone to agree with band decisions. Your advice on this would be greatly appreciated.

TLDR: The bassist in my band does not want us to add a second guitarist but the drummer and I do. How do we convince him to let us at least try some people out?
have him explain his point coherently ask him how having a second guitarist would detriment the rest of the band theen explain your reasoning which makes alot of sense having another guitarist to help with leads or even with the rhythm parts while youre singing would make being in the band alot easier

if he still says no to at least trying it then hes to stubborn for me who doesnt know him to provide any more help
.....here´s the funny thing about your voting system...

....you all took a vote and one of you decided that the rest of the band didn´t need a second guitarist?

Now I´m a firm believer of the fact that a band needs to be driven by a dictator... a kind and understanding dictator but nonetheless a "ruler of one" (kitchens and bands are and should be treated like pirate ships)...if this guy is a dick well then he usually ends up as a one man band but if this man is fair & just...then 2/3 of his band will like him at most times

...(you see how i did that 2/3 thingy as a referens towards your vote and reflecting it too why you should alway´s lean toward the "majority" whether it "yea or "neah" seeing that your looking at firing the "dictator" in your band....pretty nice huh)
I believe in god, jesus and the holy ghost.....or as i call them Angus, Kirk and Lemmy
He needs to articulate his feelings otherwise you can't discuss to come to a decision.

So if he won't do that then the majority rules. If he doesn't like that then he needs to articulate his reasons why so you can discuss to come to a decision.

If he won't do that then... you get the idea...
Don't have guys come waste time trying out and learning your material if you have not actually decided to get a second guitarist. I have gone through this, it sucked.