Remarkably, this principle has been applied and contested for seven-hundred years, though the metaphor of the Razor itself surfaced after Ockham's death.

To that, one might reasonably ask if Ockham's Razor is still a useful principle when it comes to science.

When Sagan convinces someone to come look at the dragon, the visitor opens the garage door and finds nothing there.

The visitor suggests setting up an infrared camera to catch the thermal emissions from the dragon's breath, but Sagan's dragon gives off no heat.

The visitor then suggests layering the floor with flour to detect the movement of the dragon, but Sagan's dragon floats serenely, leaving no footprints nor stirring the air.

At this point, most would agree with the visitor's logical conclusion: Sagan's invisible, floating, thermally-neutral pet dragon is a fiction.

Ockham's Razor cuts through the chaff of Sagan's dubious explanations to suggest that given the state of the evidence – an empty garage – the most prudent interpretation is that there is no dragon.

The essayist and science writer Philip Ball points out that Ockham's Razor has been used both to advance the "Many Worlds" interpretation of quantum mechanics as well as to critique it?