Always ask "why" about punctuation rules

A student asked: I am wondering if you have any advice on avoiding the comma splices that I seems to create without realizing it? Apparently, I am horrible at following semi-colon/ comma rules.
 

What is a comma splice? It's usually a two-independent-clause sentence (two subject-verbs) with just a comma connecting them. The question is, why is it an error just to have the comma?

(I'm not going to get into the exceptions here, as they're just confusing... again, when we know the rules, we'll know when to break the rules. So ask me later and I'll see if I can figure out a good example of an exception and the reason for it.)

So let's think through the sort of sentence that would generate a comma splice.
"Two independent clauses" means that each could be a sentence on its own. We've just chosen to put them into one sentence. 
Let's make that one sentence, just to illustrate:
"Two independent clauses" means that each could be a sentence on its own, we've chosen to put them into one sentence. (THIS IS A COMMA SPLICE, BY THE WAY. I'M JUST DOING THIS TO ILLUSTRATE THE JOINING OF THE SENTENCES.)

See how we've taken two sentences and put them together. My first point is that we don't HAVE to join them! They're perfectly fine as two separate sentences. (And there's no danger of a comma splice if we keep them separate.)

So that's the central issue. Why did we put these two sentences together, risking a comma splice or a too-long sentence or some other problem? We did that, presumably, because there's some extra meaning or understanding if they're put in one sentence. And that little extra meaning is conveyed when we link them... but just linking them  isn't enough to get that meaning across. If all we're going to do is replace the period with a comma, we aren't indicating in the new sentence what the meaning is-- what the CONNECTION is. 

And that's shown not in the punctuation but in the addition of the connective word, the "conjunction." The most common conjunctions are abbreviated in the acronym FANBOYS: for (meaning because-- the old meaning), and, nor, but, or, yet, so. (For, nor, yet are kind of old-fashioned, but I think they're needed to make that acronym a word. :)

"For" implies a causal condition (Clause A happened because of Clause B).
"And" implies addition (Clause A and Clause B both happened the same time or way).
"Nor" implies negation (neither Clause A or Clause B is true).
"But" implies contrast  (Clause A and Clause B are in some conflict).
"Or" implies alternation  (either Clause A is true or Clause B).
"Yet" is another contrast like "but".
"So" is causal like "for," but in the other direction ( (Clause A causes Clause B to happen).

A comma splice is incorrect NOT because this is an arbitrary rule, but because without the conjunction, the reader won't know how these two clauses connect. Without the conjunction, the reader won't know what we're supposed to make of them together. This is really important when there's a contrast or a cause. The reader shouldn't have to puzzle about whether the author is confused and just doesn't know that the clauses conflict with each other -- I like blue best, (but) I chose a red car-- or that one causes the other -- Mary forgot Joe's birthday, (so) he forgot Valentine's day. Put in the doggone conjunction to show that you know what you're implying.

So let's go back to that first pair of clauses, and let's think about what the connection is:
"Two independent clauses" means that each could be a sentence on its own, (conjunction here) we've chosen to put them into one sentence. 
What conjunction would you put in there? ABOS? (I've taken out the old-fashioned ones, and you can see it's not as good an acronym!) And? But? Or? So? Which of those words best implies the linkage? (Read it aloud, and I bet you'll "hear" the right one.)

See, it's the conjunction more than the comma which adds meaning. The comma is just a substitute for the period that would be there if these were still two sentences. The conjunction is important, and yet, that's the element that's dropped in a comma splice. So don't think of a comma splice as a comma problem. It's a MEANING problem. There's a missing word that supplies meaning. Add that conjunction, and you add meaning (and oh, yeah, you fix the comma splice).

Now of course, you can also use a semicolon! And that might seem like a simple way to "fix" a comma splice. But it's not... because the problem with a comma splice isn't the punctuation! It's the missing conjunction. Just putting in a semicolon to replace the comma makes the sentence grammatically correct:
"Two independent clauses" means that each could be a sentence on its own; we've chosen to put them into one sentence. 
But it doesn't make the sentence more meaningful. It doesn't tell the readers how to connect these two things in their minds. Only the conjunction can do that. (Notice that the adverbial conjunctions like "however" and "moreover" are just synonyms of the usual conjunctions-- "however" means "but," "moreover" means "and." For a couple reasons I can only speculate, we use the semicolon with them.)

Why then-- meaning-wise-- would we use a semicolon rather than the more meaningful conjunction+comma?
Two situations:
1) When the linkage between the two clauses is completely and absolutely clear without a conjunction: I went to the store; I needed milk. However, I would not use a semicolon for some lame sentence like that, just because semicolons tend to stick out and are often considered "stodgy" and "too formal," so they should be used sparingly. (Some editors think they should always be edited out, by the way. We call this disagreement The Great Semicolon War, and I have to say, I'm a combatant on the "let's keep semicolons" side.) 
2) When the writer wants the connection to be presented as ironic, without spelling it out. Mary forgot Joe's birthday; he forgot Valentine's day. The reader is supposed to figure out that, you know, Joe didn't actually forget, that he did that deliberately. Again, less is more. I'd do this only when I wanted to force the reader to figure out what I'm implying.

Anyway, just remember... the problem with a comma splice is that a sentence like that is missing the conjunction, and the conjunction adds the additional meaning that should come when you put two clauses together rather than leaving them on their own. Think "connection," not "comma" here. It's not an arbitrary rule, but a guideline meant to guide us to the greater meaning.

Does that help, or just confuse things more?
Alicia