Step one of quantifying the uncertain involves embracing the absurdity of existence. It's like trying to measure the squishiness of a jellyfish.
Start by defining your variables: X for the unknowns, Y for the unknown-unknowns, and Z for the completely-made-up variables.
Now, take a deep breath and attempt to assign numerical values to these abstractions. Don't worry, it'll be a real challenge, like trying to count the number of raindrops that make up a rainbow.
Proceed to Step Two: Where the math gets really weird.
Appendix: A brief history of failed attempts at quantifying the uncertain.
Or, if you're feeling adventurous: Experimental Section: Where the math gets even weirder.