Bernard Krasner (plaintiff) and Morton Berk (defendant) were doctors who shared an office space, splitting the rent equally. In September 1967, Berk’s wife and brother observed changes in Berk’s behavior. Berk had become forgetful and disoriented, neglecting his paperwork and missing his patients’ appointments. The following year, Berk began to talk with doctors about his health. By 1969, Berk would forget his car and hitchhike home. Berk missed more appointments and had other troubles. Berk’s wife talked with Krasner about these issues, but Krasner replied that he saw no change in Berk. In April 1969, after an unsuccessful search for a new office space, Krasner and Berk renewed their lease for three years. In a second agreement, written by Krasner’s attorney, Krasner and Berk stated that they would share the rent and taxes equally even if one of them left the office space for any reason, including disability. Berk read the agreement and said that it was fair. Berk also later dictated a letter complaining to the landlord. In June 1969, Berk saw a neurologist, who found that Berk was having short-term memory problems. Later that year, the neurologist found that Berk’s issues went beyond memory. Berk had presenile dementia, which had developed slowly and was irreversible. The neurologist advised Berk to stop practicing medicine, which Berk did in July 1970. Krasner sued Berk for Berk’s half of the rent and taxes under their 1969 agreement. At trial, Krasner asked the court to find that Berk could not raise a mental incapacity defense because Berk understood the agreement at the time it was made. The trial court denied Krasner’s motion, but the appellate court reversed. Berk appealed.