Bumbo sat motionless in the Temple of Meaning. His teacher asked what he was doing.
“I am learning to use commas,” Bumbo told him.
“You foolish student,” the teacher exclaimed. “If you do not act on what you know, your life will never be complete.”
Bumbo, the subject of this koan, isn’t doing anything. He thinks he is, but he is wrong. The teacher reminds him that a subject without an action is incomplete. He wants Bumbo to learn that a comma should not separate the predicate from the subject because a subject needs a predicate to make a complete sentence.
Every complete sentence needs two things: a subject and a predicate. These two parts are required and work together to make a complete sentence. The key word here is together.
Commas separate items in a sentence. The absence of a comma shows that they are connected. If we put a comma between the subject and predicate, we separate them. This is wrong because they need to be connected: they work together.
Wrong example: The author of the best-selling book on marketing, began planning his next book.
In this wrong example, the complete subject is The author of the best-selling book on marketing. The predicate, which begins with the main verb, is began planning his next book. This example is wrong because it has a comma between the subject and predicate. To fix this sentence, we remove the comma and join the subject and predicate.
The only time you can have a comma between the subject and predicate is when the end of the subject has some phrase or expression that requires a pair of commas. In that case, the commas are in the sentence not to separate the subject and predicate but to separate the phrase, as seen in the next example.
Correct example with commas: The author of the best-selling book on marketing, which he released the prior year, began planning his next book.
In this example, the comma before the main verb is part of a pair of commas to separate the non-restrictive phrase which he released the prior year. The first sentence of the explanation above also uses commas in this way.
Need help with commas? Get Zen Comma, an instructive reference guide on the 17 major uses and misuses of commas, available in PDF and Kindle formats. Read more about Zen Comma.