Occam's razor

According to Liv Chenka, Occam's razor postulated that the mostly obvious solution was usually right. (AUDIO: How to Make a Killing in Time Travel) Occam's razor was associated with William of Ockham, a figure on Earth. (AUDIO: The Lost Resort)

The Fifth Doctor felt the principle was similar to Margyle's knife, which originated on Traken. (AUDIO: The Lost Resort)

Behind the scenes
In the real world, Occam's razor (aka the principle of ) postulated that the solution that had the least number of entities, i.e. that which was most simple, was most likely right. The term is derived from William of Ockham, a theologian who was well known for his skepticism of abstract entities outside of God.