How should the punctuation work for “and, therefore,”?

Question

I'm unsure where to place the commas:

[some argument], and, therefore, [blah blah].

or is it

[some argument] and, therefore, [blah blah].

or is it

[some argument], and therefore, [blah blah].

or none of the above?

Answer 1

It’s difficult to say for certain without seeing an actual sentence. However, a comma is frequently used before and when it joins two clauses, (see?) and, since therefore is a weak interruption it, too, (like too, see?) may be set off by a pair of commas. That background suggests that the first solution might be the most appropriate one.

Answer 2

Since the "Therefore" introduces a sentence that stands on its own, I would suggest none of the above, but rather:

All men are mortal. Socrates is a man. Therefore, Socrates is mortal.

Here is an example of this syllogism.

Answer 3

I would use a semicolon before therefore, and no comma after:

[some argument]; therefore [blah blah].

See this Grammar Girl post on how to use semicolons and conjunctive adverbs, such as therefore:

Semicolons with Conjunctive Adverbs and Transitional Phrases

Finally, you use a semicolon when you use a conjunctive adverb or transitional phrase to join two main clauses.

Conjunctive adverbs are words such as “however,” “therefore,” and “indeed,” and they "usually show cause and effect, sequence, contrast, comparison, or other relationships" (1). For example, “I have a big test tomorrow; therefore, I can't go out tonight.” (The comma after the conjunctive adverb is optional.)

A transitional phrase is something like “for example” or “in other words.” A sentence with a transitional phrase could read as follows:

I have a big test tomorrow; as a result, I can't go out tonight.

Coordinating Conjunctions Versus Conjunctive Adverbs

Sometimes people seem frustrated because they have to remember to use commas with coordinating conjunctions and semicolons with conjunctive adverbs most of the time. If you can't keep the difference straight in your head, it can help to remember that commas are smaller than semicolons and go with coordinating conjunctions, which are almost always short two- or three-letter words—small words, small punctuation mark.

Semicolons are bigger and they go with conjunctive adverbs and transitional phrases, which are almost always longer than three letters—bigger words, bigger punctuation.