Can there be a mistake as to the identity of another party? Which of the following is correct?

		Mistake as to identity cannot void a contract since it is the subject matter of the contract which is essential
		Mistake as to identity will only void a contract where the other person in fact did not exist
		Mistake as to identity will always allow the rescission of a contract since a contract is a meeting of the minds, wrong identity means no agreement
		Mistake as to identity depends on the circumstances, if identity is not relevant, then the contract remains intact, if in fact identity is important and another party is taking advantage of anothers belief, then the contract may be void