From Galatians, we know Paul departed twice from Damascus, but were both departures also escapes? A common argument against the "two escapes" hypothesis is simple incredulity that Paul would try the same trick twice, but I'd invite all such skeptics to try on this quick thought experiment.
For starters, let's assume, as a great many do, that Acts 9 and II Cor.11 refer to the selfsame event. That is, let's assume Paul escaped from Damascus only once. Now, for this experiment, let's assume that the *one* escape happened to fall at the first departure. The only circumstance we need to remember is the one circumstance common to both Acts 9 and II Cor.11 - that Paul was let down from the wall in a large basket.
Remember, thought experiments like this can be well worth your time. But this one will be quick. I promise!
Alright. Paul's first Damascus departure was an escape. Here is point one: the escape was effective. Well, duh, you might say. Obviously Paul wasn't caught. Yes, but it's more than that.
If Paul had been seen going down from the wall, he'd have been caught by the time he touched ground. If Paul had been spotted so near to the wall, he wouldn't have gotten away. The fact that Paul got away means that - if Paul was spotted - he at least wasn't spotted so near to the wall. Therefore, the fact that Paul got away means that no one saw his particular method of escape, at that moment, when he was coming down the side of the wall. We should further presume the Damascene brothers pulled that basket back up. If they'd left the basket and rope on the ground, any sentries patrolling the wall would have been only a few minutes behind him, at worst.
So, Paul's escape proves that the trick had proven completely effective, and more importantly, that the trick had remained, to that point at least, entirely secret.
Now, Paul goes down to Arabia, where he may or may not have gotten himself in some trouble, because of course, it's very like Paul to get himself into trouble wherever he travels. And then Paul comes back up to Damascus, where he's somewhat if not even more likely to get himself in new trouble, although we don't normally hear of Paul getting himself into trouble the second time he passes through a particular town (cf. Lystra, Iconium, Antioch-of-Pisidia, Thessalonica, Corinth, Philippi, Troas, Ephesus, etc. But not Jerusalem. Hmm.) At any rate, Paul being Paul, let's suppose even odds that Paul gets himself back into trouble again, on this return trip to Damascus.
Now, supposing Paul needs to escape again... hypothetically... and supposing the Damascene church has another discussion about how to help Paul escape. If that had happened, twice, what do you think they'd have done?
Should we suppose they'd be more likely to come up with a new and untested idea for helping Paul to escape, perhaps for novelty? Or should we suppose they'd be more likely to favor the tried and true method which proved effective the first time, and which almost certainly had remained secret since then? In that hypothetical situation, the more likely choice should be glaringly obvious. In general, among ancient peoples, and this being quite contrary to modern sensibilities, particularly those of the well educated, novelty was grossly unvalued. Practicality trumped.
Of course, this doesn't necessarily mean that Paul therefore *did* escape from Damascus two times. What it does mean is that, logically, one should not think it less likely they'd use the same escape method twice. When one gives proper consideration, one should think it highly more likely they would use the same method as earlier, assuming escape became necessary a second time.
To go further, to actually answer the question - Did Paul escape from Damascus once or twice? - we'd have to study the circumstances in both situations and reconstruct a timeline, judging which of three scenarios were more likely: (1) escape at first departure only, (2) escape at second departure only, or (3) escapes at both departures from Damascus. (For reasons I won't go into just now in this post, I take option #3. Search this site if you want to know more... At any rate, the most common objection (to my pet view) happens to be total bunk.)
Here endeth today's lesson. ;-p