Normally, I like to have my characters completely thought out (at least major characters, minor supporting characters are ok to be more NPCish, and develop on their own as needed) including personality, motivations, goals, and backstory. I find it easier to get into their heads that way. But... I've got a character where I only have a mostly sketched out backstory, and the problem is I have him having at least one trait/goal with no backstory that explains it. It's pretty major, but... do I really need to have it? And would the story suffer for not having even hinting at the explanation? Thoughts?