Occam’s razor provides a practical guiding principle whenever someone sees a light or object in the sky that they can’t identify—by definition an unidentified flying object or UFO. We know there are a host of natural and man-made phenomena that could result in a UFO. Invoking such explanations doesn’t introduce any new assumptions into our view of reality. On the other hand, since it hasn’t been established that an alien technological race exists and is currently visiting the Earth, invoking alien spacecraft as an explanation requires the introduction of a massive new assumption.
