Recognizing Categorical Propositions in English
 

Many categorical sentences in English can be recognized and classified easily. "All mammals have hearts" is clearly an "A" type categorical proposition. "Some philosophers are silly" is an "E" categorical proposition.  In both cases, the subject and predicate are exactly where they should be.

Let's look at some harder cases:

Clearly this is the negation of an A-type categorical proposition. But we know that the negation of an A-type categorical proposition is logically equivalent to an O-type categorical proposition. So if we are asked which type this example corresponds to, of our four categorical proposition types, the correct answer is that it is an O-type categorical proposition.

  How do we treat this? To answer we ask: Is it universal or particular? Is it affirmative or negative? What is the subject and what is the predicate? Clearly this is proposition is particular and affirmative. The subject is potatoes, and smallness is being predicated of the small potatoes. So we can rewrite this as "Some potatoes are small."

and this is an E categorical proposition.

Consider the following sentence:

Before we ask whether this is this universal or particular, affirmative or negative, we need to ask what our subject is. Is this about jazz musicians or about cool people? It is saying that only jazz musicians are cool. Is it saying that all jazz musicians are cool? Clearly not. So it is saying that all who are cool are jazz musicians. So it is an A-type categorical sentence which we rewrite as:

As a rule, when you see "only" by itself at the start of sentence, the sentence will be universal and affirmative. But you will need to reverse the order of the terms to get the subject term in the correct position. However, consider the following sentence:

This begins with "the only" which functions quite differently than "only".  Here we have another A-type categorical proposition, but the order of the subject and predicate here is not reversed. The correct rendition of this sentence is:

Here's an advanced exercise for recognizing and rewriting categorical propositions.