Homology, analogy and metaphor. Science in Society 5.


‘Much scientific argument and hypothesis-making proceeds through the use of analogy and metaphor’. Steven Rose.

To help us understand a scientific process we often liken it to something we’re already familiar with. We use homology, analogy and metaphor.

A homology implies identity and a common origin or shared history, eg: the bones of the font feet of a horse are homologous to those of the human hand.

An analogy implies a resemblance between two phenomena but accepts that this is only partial, eg: the blood in animals has a similar role to sap in plants. Often analogy is only metaphor and the likeness we imagine is poetic rather than exact.

A metaphor doesn’t imply any identity of process or function, but offers a new perspective on things. It help us think about our subject but it may also be a hindrance as it can limit the way we think. A metaphor brings baggage with it which can shape the way hypotheses and experiments are designed. We often use metaphors which simplify because we think they will help us understand better. There is a temptation to rely on mechanical or industrial metaphors for living processes. The metaphors and analogies we find attractive are loaded with cultural values which reflect our experience. It is a mistake to treat analogy or metaphor as homology.

A simile is where two things are directly compared because they share a common feature. The words ‘as’ or ‘like’ are used to compare the two things.


Pick 3 of the following statements about scientific ideas and for each one say how it might help us understand a process and how it might also hinder our understanding. Be as precise as you can in pointing out the accuracy and limitations of these analogies or metaphors.

  • The solar system is like a clock
  • Light waves are like sound waves
  • The atom is like a billiard ball / a plum pudding…
  • Electrons are like planets orbiting the nucleus which is like the sun
  • Electrons are waves / particles
  • Electrical current is like the flow of water
  • Genes are a code
  • Evolution is the survival of the fittest
  • Cells are building blocks
  • Hormones are messengers, homeostasis is like a thermostat
  • The heart is a pump
  • The brain is like a computer
  • Dealing with infection is a battle against germs which attack our body
  • A mammal’s limbs are like an insect’s legs
  • A plane’s wings are like a bird’s wings





About Eddie Playfair

I am a Senior Policy Manager at the Association of Colleges (AoC) having previously been a college principal for 16 years and a teacher before that. I live in East London and I blog in a personal capacity about education and culture. I also tweet at @eddieplayfair
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