Medical Investigator: "Podiatrists initially assumed that Meyer's Rash, an itchy rash between the toes, was a fungal infection similar to athlete's foot. At first, only Dr. Pannikar argued that Meyer's Rash was viral in nature. All anti-fungal medications proved utterly ineffective in addressing Meyer's Rash. Now, recent antibody studies seem to suggest, quite surprisingly, that Meyer's Rash is caused by a virus."
In the medical investigator's argument, the portion in boldface plays which of the following roles?