Alyssa was a severe schizophrenic who had to be institutionalized. Alyssa's cousin, Marlene, told Alyssa that she would buy her house for $10,000. Alyssa agreed and Marlene gave her the $10,000. Just as she was going to take possession of the house, Alyssa's brother stepped in and claimed that there was no contract between Alyssa and Marlene. The matter went to court and the court agreed with Alyssa's brother, stating that there was no contract due to one missing element. The missing element is: _______.