Summary on Occam's razor
Topic: Occam's razor
by Claire, 2018 Cohort
Note: This entry was created in 2018, when the task was to “summarise a key reading”, and so may not represent a good example to model current primer entries on.
What is Occams Razor?#
Entities must not be multiplied beyond necessity- William of Ockham, 14th
Variations of this statement have been used by some of the brightest minds throughout the centuries to solve problems and unravel complexity. Users include physicists, chemists, mathematicians and philosophers such as Galileo, Newton and Einstein.
Occams Razor (OR), also referred to as the Law of Parsimony, is a heuristic device that can be used to strip an argument or solution of excess assumptions and conditions. It is this idea of removal that lends the term razor to the tool. The theory suggests that if presented with many equally viable explanations to a problem that use all the available evidence, we should select the simplest explanation.
OR is stated in several ways and therefore interpreted in many. For example, in 1687, Newton stated, We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances and in 1963, Albert Einstein wrote The grand aim of all science is to cover the greatest possible number of empirical facts by logical deductions from the smallest possible number of hypotheses or axioms.
The key, common thread between these statements is the idea of tending towards simplicity. Simplicity, however, is a vague term that can be complex to define. There are two key and distinct types of simplicity defined in the Stanford Encyclopedia of Philosophy, described below in layman’s terms:
Syntactic simplicity (elegance): the number and complexity of hypotheses, i.e. readability or linguistically simplicity.
Ontological simplicity (parsimony): the number and complexity of things postulated, i.e. the number of moving parts or assumptions underpinning a theory. OR is often stated in a way that blends elegance and parsimony and hence it can be hard to deduce the type of simplicity that a variant of the principle refers to. This can be problematic since an increase in elegance may cause a decrease in parsimonious simplicity. If this happens, are we really tending towards simplicity and is OR of any use? The intricacies in the way that OR is denoted and interpreted is a crucial limitation of the tool and highlights the need to apply it appropriately. Complex ideas can be hidden in simple statements.
Addressing complexity with OR#
Firstly, OR is a guiding principle and not a law. It is easy to oversimplify OR and assume that the simplest answer is the correct answer. A more appropriate interpretation of the principle is that adding layers of complexity to form an argument or solution should be avoided if a simpler argument of the same quality is available.
Secondly, the user should recognise the underlying assumptions and conditions in a seemingly simple statement (note that these simple statements are elegant but not parsimonious). For each necessary condition, a theory becomes increasingly complex and less likely to be the correct solution.
By keeping these points in mind, OR becomes a highly useful problem solving tool.
References#
The Stanford Encyclopedia of Philosophy entry on Simplicity was used to construct this summary. It provides a detailed description of the notion of simplicity: Baker 2016, Simplicity, viewed 16th March 2018, https://plato.stanford.edu/entries/simplicity/#OthIssConSim.
Disclaimer#
This content has been contributed by a student as part of a learning activity.
If there are inaccuracies, or opportunities for significant improvement on this topic, feedback is welcome on how to improve the resource.
You can improve articles on this topic as a student in "Unravelling Complexity", or by including the amendments in an email to: Chris.Browne@anu.edu.au