A solipsist, to oversimplify, is the ultimate skeptic. To a solipsist, empiricism is bogus. An independent reality cannot be logically proved to exist, and even the past could be an illusion that merely accounts for the present state of mind of the observer. The only thing a solipsist is certain of is personal subjective experience–I think, therefore I am and everything else is hearsay.
So what is the opposite of this position? Well, to admit the idea that everything that is logically consistent, empirically exists–sort of a super-platonism.
I think both of these positions have problems. Solipsists have to explain why the illusion that is reality is being perpetrated. And the super-platonists (If I find a better word for this position, I’ll revise this post. And by the way, I pointed to something like this before.) have to explain why we are experiencing this particular reality an not some other–a sort of generalization of the “why this particular subjective experience and not some other,” question.