7.4 Resisting analogies


Analogies are an essential tool of philosophical and critical reasoning, and often play a central role in philosophical thought experiments. A simple analogy notes that two things are similar in some respect, and thus what can be concluded of one in some domain, can also be concluded of the other in the same domain. For example, I might notice that babies tend to stick out their tongues in response to adults sticking out their tongues. From this, I might reason by analogy that if an adult waves a hand, a baby should respond by also waving a hand.

However, the success or appropriacy of analogical reasoning depends entirely on whether the cause of the first case is also operating in the second case. Importantly, the cause must not only be operational in the second case, but not defeated by any other factors. In our baby hand-waving example, my analogy could easily be defeated by realising that the muscular effort to push out a tongue is far less than that required to wave a hand. Very small infants may not have the muscular power for hand-waving, so my analogical reasoning could well fail because of a significant difference between the two cases that I didn’t notice.

Arguing by analogy is something we do naturally all the time, but it takes some skill – a bit of lateral thinking in fact – to weigh up analogies and spot errors of reasoning.

Try the following exercise, which relies on an argument by analogy.

Exercise 7.4

In the blockbuster movie ‘Hulk’, Bruce Bana plays a tortured doctor trying to unlock the secrets of regeneration. Although ‘Hulk’ might be science fiction at the moment, regeneration is something we are all familiar with. If a tree or shrub is cut off near the ground, new shoots may spring up from the stump. Among animals, simple worms, sponges, and cnidarians such as jellyfish, coral and sea anemones show remarkable powers of regeneration. They can be cut in pieces, and each piece can grow into a new animal. Starfish can grow new arms. Crayfish can grow new claws, eyes, and legs. And what about people? Is ‘Hulk’ possible? If you think it’s all just science fiction, remember that people and other mammals regenerate hair, nails, skin, and a few other tissues all the time. In some cases, a completely different sort of tissue grows over a damaged area and forms a scar. While none of us can grow limbs or increase our size, the process of regeneration is quite a natural one. Perhaps in this age of genetic engineering, the storyline of the hit movie is not so fanciful after all.

Type of argument: ___________________________
Claim: _______________________________________

It is a good / bad argument because _________________
_____________________________________________________
_____________________________________________________
_____________________________________________________

When you are ready, check out the answer and explanation here.

Alternatively, continue reading

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