Sir, - It seems to me that the frequently used idiom "that's what" - especially in the light of the utter unanswerability of its naturally provoked question: "what's that? - must surely rank highly among similar, positively pointless phrases such as: "at this point in time", "how and ever", "at the end of the day", etc., that trip so trippingly to the tongue!
However, on the other hand, it may very well serve as a mighty mantra in moving one's though processes to a meditative state where, freed from the tediousness that sometimes attends reasoning, one rests at a still point of inner being.
Wherefore, what with oodles of such exclamatory whatnots or what have you, and if that's what and that's not what and all that - and, what is more, if that won't do for what, one is inclined to say "what of it?" stop at that and cherish its inherent absurdity as a gem among mantras of the world! - Yours, etc.,
Beach Park,
Laytown,
Co Meath.