Astronomer: Astronomical observatories in many areas have become useless because light from nearby cities obscures the stars. ████ ██████ █████ ████ █████ ████████████ ███ ██████ ███ ███████ ████ ████████████ ████ ██████ ██ ███████████ ████ ██ ███████████ ████████ ███ █████ █████████████ ████ ███████ ██████████ ██████ █████ ███ ████ ███ ██████████ ███████████ ████████ ███ █████████ ███████ ██████ █████ ████ ██████ ███ █████ █████ █████████ ██ ██ █████████ ████████ ██ ████ ████ ████████████ ███████ ███ ██████████ ████ ██████
The astronomer introduces a problem: many astronomical observatories are no longer useful because light from cities nearby interferes with the view of the stars. Some people say that this problem of light interference is inevitable, because streetlights are necessary for safety.
But the astronomer disagrees. She points to Sandsville, where restrictions on unnecessary lighting and the installation of special downward-directed streetlights have allowed the city both to have streetlights and to keep the view clear for the local observatory. From this example, the astronomer concludes that it is possible to have both well-lighted streets and keep the skies clear for observatories. The problem of light interference isn't inevitable.
The astronomer counters a position held by others: the idea that it is "inevitable" to have light pollution from cities interfere with observatories, since streetlights are necessary for safety. She responds to this position with a counterexample, pointing to Sandsville, which keeps its skies relatively dark by restricting unnecessary lighting and using special street lamps. This example disproves the claim that city lights will inevitably interfere with the view for observatories.
The astronomer's argument proceeds by
appealing to a ██████████ █████████ ██ █████████ █ ██████ ████ ██████
questioning the accuracy ██ ████████ █████ ██ ███████ ██ ███ ████████ ████████
proposing an alternative ██████████ ███████████ ███ █ ███████ ██████████
making a distinction ███████ █████
offering a counterexample ██ █ ███████ █████