Strange little theme of finding an old SAW - "Still waters run deep" - in the first words of four theme answers. The theme answers themselves are all common enough, although I tend to associate DEEPTHOUGHTS (52A: "What is life?," "Why are we here?," etc.) with comedy rather than philosophy, thanks to one Mr. Jack Handy, whose DEEPTHOUGHTS run more like this:
If God dwells inside us, like some people say, I sure hope He likes enchiladas, because that’s what He’s getting!ORLON is a lousy word (coined in 1941 by Dupont) and a lousier fabric. Synthetics release hundreds of thousands of microparticles into the water stream each time they are washed. You may think the shirt is CLEAN, but it makes the EEL and his friends DOUR. Kind of takes the SHEEN off of all those artificial fabrics, eh?
I enjoyed SMOLDERS (4D: Burns slowly) and its neighbor AIRKISS (5D: Simulated smooch), and maybe I'm just giddy, but the clue for GIANT (39A: "Fee-fi-fo-fum" sayer) also made me chuckle. KEENLY (44D: With enthusiasm) is nice, and I prefer seeing AEIOU (33D: "Wheel of Fortune" purchases) to the singular "an o" or "an i" any day.
Overall, I thought this was a perfectly serviceable Monday.