One of the first duties of the physician is to educate the masses not to take medicine.... Soap and water and common sense are the best disinfectants.

The remark encapsulates Osler’s characteristic therapeutic conservatism and his emphasis on prevention. He urges physicians to counter the public’s appetite for pills and potions by teaching restraint—many ailments resolve without medication, and unnecessary drugs can do harm. The second sentence shifts from treatment to public health: basic hygiene (“soap and water”) and practical judgment (“common sense”) do more to prevent infection than elaborate remedies. Read together, the lines reflect the late-19th/early-20th-century transition toward bacteriology and sanitation, and Osler’s belief that medicine’s moral duty includes educating patients and communities, not merely prescribing.