Posted by: Bystander PJ4 APR 2012
On 10 April the Church of England commemorates a 14th century Franciscan friar and scholastic philosopher who is considered a major figure of medieval thought. His name was William and he was born in about 1280 in the hamlet of Ockham, near Woking in Surrey. He is therefore described as William of Ockham.
William is mainly remembered for the methodological principle now known as Occam’s razor, from an alternative spelling of his birthplace. Essentially, this says that when trying to understand a new phenomenon the simplest explanation is usually the best. William used a metaphoric razor to slice away any assumptions that made no difference to the outcome of a hypothesis.
Occam’s razor is still used in many fields of thought, including science, religion and philosophy. It has an important role in medical diagnosis in the guise of “diagnostic parsimony”. This advocates that when diagnosing an illness or injury you should initially look for the fewest possible causes. You should also look first at the most likely causes, as illustrated by the statement: “When you hear hoofbeats, think horses, not zebras” (an adage that has resulted in the slang use of “zebra” for a wacky diagnosis from ordinary symptoms).
Of course, Occam’s razor does not mean that unlikely explanations should be ignored altogether. Nowadays diagnostic parsimony is balanced by a principle known as Hickam’s dictum, which states: “Patients can have as many diseases as they damn well please.” This maxim, attributed to John Hickam, an American academic physician active some 50 years ago, acknowledges that multiple symptoms may indicate several concurrent common diseases rather than a single obscure one.
It seems that in healthcare the truth may well lie somewhere between Occam and Hickam. It is best to pursue all reasonable theories, even though one theory may appears the most likely.