(Pardon all this commentary please, but, before accusations of bias, of course I love Abbott and Costello, however, this is not why I wrote this post - let this post be the reason why I love Abbott and Costello.)
No doubt, all of you have at some point heard, seen, or otherwise witnessed some of the "humor of the modern man," as my father once put it - it is occasionally amusing, but on a whole rather dependent upon the base, noisy, and slapstick (or things less clever and subtle even than slapstick, as often is the case). Most of the humor is either identity humor ("I'm funny because I'm..."), shock humor ("that's funny because it involves that uproarious, surprising, or gross thing") , or put-down humor ("that's funny because it insults someone or something we all generally dislike or disapprove of around here"). It's all based on thinking a thing is funny only because of a certain viewpoint, rather than something that is inevitably and universally true.
(Just as a warning, I shall be quoting dear old Mr. Chesterton a lot in this post, as Mr. Chesterton and I get along quite swimmingly... All quotes are taken from Heretics, I believe.)
Really, truly good comedy is based on two things - the first and foremost of these is basic truths of life. The truth is, life is funny; odd things happen, coincidences happen, and nothing seems to make sense at face value. Thus, if reality is a funny thing, it is no coincidence that humor is based off of a discovery of reality and the truth. Nowhere will anyone claim that the truth always is convenient or sensible-sounding. Oftentimes, it's not, and to our limited human understandings, it seems like the silliest and strangest thing. Thus enters humor. And thus enters the second aspect of humor, almost as important as the first and even more integral in humor's nature: humility.
Humility and humor really do go hand in hand. I mean, really, they even have the same root word. Humor is the manifestation of humility; it is the taking of joy despite and in spite of human flaws. We are imperfect, and that's what's so funny. The moment we take ourselves seriously, that is the moment we sin and become prideful. In taking ourselves seriously, we pretend that we are really worth something on our own, that we are respectable and praise-worthy, and that we really know what we're doing. Well... do we...? No, not usually, at least - we human beings almost never really know what we're doing properly. And most of the time, when we think we know best is when we make our worst and most regrettable decisions. Laughing at ourselves is the quickest way to route pride and grow humility because it admits to us that we really are strange, funny, awkward things, and we have no idea what to do and no power to do it on our own.
Good comedy is good for the soul.