Assume that a person lacks the mental capacity to enter into a contract, but appears to strangers to be normal, as in many cases of dementia and other mental illnesses. If that person enters into a contract with a stranger, and the stranger doesn't know that the person lacks capacity, can the stranger sue for breach of contract? Does the stranger have any ability to recover? How is a stranger supposed to know that the person lacked mental capacity in order to avoid this problem?