When does a comma precede "because"?

Question

I know a similar question was asked before, but I didn't understood it (call me stupid or idiot).(Comma before "because.")

As it is evident from this site that a comma must precede the conjunction before but only when there are two meanings.

Question: What did you like about camp?

Answer: I liked swimming and hiking because they were fun.

Does he need a comma before because they were fun?

The short answer is no.

Another example is given where it is advised to put a comma before because:

• He didn’t run because he was afraid.

Without a comma, you don’t know whether the writer means that the reason the man didn’t run was that he was afraid or whether the writer means there was some different reason the man didn’t run.

If you put a comma before because (He didn’t run, because he was afraid), it’s clear that the part after the comma is extra information: the reason the man didn’t run—because he was afraid.

Isn't it obvious that he didn't run because he was afraid? Just like the first example it was obvious that he liked swimming and hiking because they were fun?

Can anyone please illuminate this matter to me in simple terms?

Answer 1

The second sentence is ambiguous: it might be interpreted two different ways. The presence or absence of the comma determines how it is interpreted.

• With a comma, because he was afraid is outside the scope of the not: it tells why He did not run. This version may be paraphrased

  The reason that he did not run was because he was afraid — he was immobilized by fear.

• Without a comma, because he was afraid is inside the scope of the not: the sentence denies a possible reason why He did run. This version may be paraphrased

  The reason that he ran was not because he was afraid — he ran because he was in a hurry to do something else.

The use of the comma to distinguish these two meanings reflects the stress contour in speech.

• In the version with a comma, He did not run is an independent clause, marked by peak stress on run with a falling intonation. This cadence would ordinarily be marked with a full stop, but with because he was afraid tacked on as a 'supplement' the disjunction is marked with a comma.

• In the version without a comma, everything after not is a single constituent: what is denied is run because he was afraid. Consequently there is no cadence on run, and only secondary stress, and the flow runs continuously from run to afraid, so there is no disjunction and therefore no comma.