Anatomical bilateral symmetry is a common trait. It follows, therefore, that it confers survival advantages on organ...
kearannMay 5, 2020
Difference between principle rule and premise
As I am going through these, I am continually getting confused on the difference between a principle rule and a premise. I understand that in transitive instances, the premise can have both a sufficient and necessary component, but in this question the premise is just one part. How do we know if it is a premise or the general principle? I would love a bit of clarification on this. And are general principles common to only these types of problems? I do not remember learning about them in the other logic lessons thus far.
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I'll start by breaking down this argument, and then we can discuss principles and premises in general.
Premise 1: Anatomical bilateral symmetry is common.
Premise 2: If bilateral symmetry did not confer survival advantages, it would not be common. not CSA ----> not C C ----> CSA
We were given C, therefore we can conclude CSA.
Conclusion: Anatomical bilateral symmetry confers survival advantages on organisms.
We are given a piece of information (premise 1), followed by a principle rule (premise 2). Combining these premises leads to our conclusion, which is valid. Remember that we are to accept that premises are true.
To your question. You acknowledged that there are premises with a sufficient and necessary component. So, you should be able to see that a principle can be a premise! Very frequently, a principle is nothing more than an if/then statement, or sufficient followed by necessary. Principles are well suited for this type of diagramming: X ---> Y. There is no general rule for distinguishing principle from premise. You have to consider the argument structure. "It follows, therefore..." from this question is a strong conclusion indicator. We can see that the rest of the stimulus supports this conclusion. I'll give you another example.
P: If a new neighbor moves into the vacant apartment, they will have to respect the smoking ban. (premise/principle rule) P: Billy will move into the vacant apartment in June. C: Therefore, Billy will have to respect the smoking ban.
This is the same structure as the question above, in which the principle acts as a premise. Again, we accept premises as true. However, a principle can be a conclusion as well, in which case we do have to evaluate its validity.
P: My neighbor Billy drinks beer every Saturday. P: My neighbor Billy is a gambler. C: Therefore, if you drink beer every Saturday, you will become a gambler.
Obviously, this principle does not follow from the premises, making it an invalid conclusion. In short, a principle can have a variety of roles in an argument. You must consider the argument structure to identify conclusions and premises.
jnewtonMay 22, 2020
I had a similar question, and this explanation was helpful. I'd clarification on a more specific point: We diagram "anatomical bilateral symmetry is a common trait" as "CT" but why can't we diagram it as:
Anatomical Bilateral Symmetry --> Common Trait ( ABS --> CT )
This is similar, from what I understand, to the example "A carrot is a vegetable." (C --> V) Not just, V. Can you elaborate?
lsatstudier1July 31, 2020
Bumping this question^^^.
Would it also be possible to diagram it as ABS = CT? Or would you recommend against that?
