YES and NO. At any rate you DO need a training partners that you can try you technique out on. People did creat martial arts. They didn't alawys exist. So, yes, one CAN teach themself, but it is always best to seek instruction under a good, competent, knowledgeable instructor.
Think of it in terms of mathematical systems. It's going to be hard to invent calculus with just a basic knowledge of numbers. It's better to go to college and work your way to it. Same thing with martial arts.
"One Mind, Any Weapon"