Many doctors cater to patients' demands that they be prescribed antibiotics for their colds.
Conclusion (so / should)
Doctors should never prescribe antibiotics to treat colds.
Intermediate Conclusion (so)
Antibiotics have no effect on colds.
Premise
Colds are caused by viruses. Antibiotics have no effect on viruses.
Premise
Prescribing antibiotics for a cold can have dangerous side effects.
Evaluate
The argument offers two reasons why doctors should not prescribe antibiotics to treat colds. The first points out that antibiotics are ineffective against colds. And second, antibiotics can have dangerous side effects. So the operative principles seems like, .