Two things are similar in certain respects. We conclude that the two will be relevantly similar in other respects. Often they are just used as explanatory devices, but often they are also arguments. This is based on the notion that we treat similar cases similarly. Sometimes we can't decide what to say about an argument. we may want to resort to analogy, in order to make a point. The important thing will be to see that the similarities between the cases are in fact sufficient to make the case.

     Analogies in themselves are not necessarily arguments. You can make a comparison between two things for explanation. For instance, people used to think of the atom in the same way as the solar system -- one massive thing at the centre, with smaller "planets" going around. This was simply an attempt to understand, not to argue.

Argument from analogy: Using analogy to prove a point.

P1: The Primary Subject is similar to the Analogue in ways 1 to n.
P2: The Analogue has the targetted predicate.
C: Therefore the Primary Subject has the targetted predicate.


P1: PS is like A in S1...Sn.
P2: A has TP.
C: So, PS has TP.


Primary subject: the subject of the conclusion.
Targetted predicate: what is being said about that subject.
Analogue: the thing with which it is compared. Appears in both premises.
Similarities: features that connect A and PS.



My client has been charged with murder. There are similar circumstances to this case, though, in previous cases, and in those cases, the defendant has been found not guilty. Therefore, in my client's case, he should also be found not guilty.

Primary subject: The current defendent.
Targetted predicate: Defendent found not guilty.
Analogue: past defendents .
Similarities: circumstances that are similar.


P1: The current defendent is like past defendents because of various similar circumstances.

P2: The past defendents were found not guilty.

C: The current defendent should also be found not guilty.