Standard Form versus a diagram key

If you have worked through the previous lessons you may have asked yourself a couple of questions:

    1. What is the difference between Standard Form and a diagram key, and
    2. Why do I need both?


The answer to the second question is simply because they are both required by SQA's Higher Philosophy course!

Of course, there is more to be said. In one sense you don't need both because an argument diagram with a key tells you everything that standard form does plus a little bit more. A diagram tells you how the premises are working together to support the conclusion.

One way of thinking about the relationship between the two is to remember that if you reduce an argument to standard form you can always use that standard form as an argument key but an acceptable diagram key isn't necessarily in standard form.

Textbooks vary, but if we think about them in terms of SQA requirements then

    • Both require you to rewrite the statements so they are standalone statements.
    • Most commonly an argument key simply lists the statements in the order in which they occur in the original argument and then they are numbered sequentially whereas standard form rearranges the statements into their logical order and requires the final conclusion to be at the end.
    • A diagram key doesn't require an inference bar or any way of distinguishing between premises, intermediate conclusions, and the final conclusion, because all of that information is presented in the diagram itself.


The reason why both exist is because of the two different approaches to argument analysis. You will recall that the approach most commonly used in universities is called Formal Logic and the other approach is called Informal Logic. Reducing an argument to standard form has long been used in introductions to formal logic and is seen as a stepping stone to representing the argument with symbols.

So

Of course Socrates is mortal. All humans are mortal and he is a human.

Becomes

All humans are mortal
Socrates is a human
.                                                         .

Socrates is mortal.

Which then becomes

All A are B
x is A
.                                 .
x is B

Where A = Humans; B = Things that are mortal; and x = Socrates

Since informal logic isn't generally heading towards a symbolic representation of arguments it doesn't need the same stepping stone. However, there are some topics in this course where it will still be helpful to think about the underlying structure of argument in this way.