Sure, you may have invented the lightening rod which was important if you're into electricity and sciency crap. And let's not forget bifocals; without bifocals lot of people would have to ask a stranger across the street hold up a menu for them to read at restaurants. But there a few more addendums I wish to add to the aforementioned "certain things".
These certainties I feel can safely be nestled among death and taxes:
Whenever you are gridlocked in traffic, a drive-thru line, or on a stretch of highway with no stops for a zillion miles - someone will have to go potty with such urgency that you are forced to say "YOU'RE JUST GOING TO HAVE TO HOLD IT A LITTLE LONGER! WHY DIDN'T YOU GO BEFORE WE LEFT WHEN I ASKED YOU TO?" When you finally locate the nearest bathroom it is the most vile, Ebola-harboring-hole-of-hideous you have seen. You decide it would be far more sanitary to pee next to the car and wipe your cherubs ass with road kill than step foot into that giant used colostomy bag.
Whenever you take your child to the doctor's office, three days later they will be FAR more ill with something they contracted at their appointment than what you took them in to see the doctor for initially.
About 10 minutes before you leave for a major event - your child will announce that they cannot locate something critical for the event (even though you went through everything the night before to make sure they were all set and they rolled their eyes and gave an exasperated, sighing YES). For example, the love of your life will discover that she does not have her mouth guard right before you are to drop her off at lacrosse camp. You will drive around like a hellhound trying to figure out where to get another mouth guard in time. You are not above banging on the door at the Dollar general and begging them to let you in a few minutes early to spend $25 on a replacement piece of plastic. Breaking the sound barrier, you rush home to boil the shit out of that bastard, she locates the missing item and you have to restrain yourself from whacking her with her lax stick. (As a side note, it is perfectly acceptable to call your angel a "Dumbass" at that time).
Right as you are about to head out the door, dressed to the nines, your seraphim will hug you goodbye and wipe something filthy on your beautiful outfit. You're running late already due to an epic meltdown about her sister not sharing a plastic McDonald's toy. You have not one spare second to change. So you spend the entire night obsessing about the giant mess on your dress while trying to strategically place something to block it or constantly explaining how you came to this unkempt state. Or transversely, you walk around all night like you're on a catwalk, not realizing that you have spit up on your shoulder and a Handy Manny sticker of Squeeze on your ass.
Shhh...don't tell her. It's WAY funnier that way.
You have FINALLY found a dinner that everyone in your family enjoys. You spend time purchasing the items, preparing and serving that masterpiece. They will gag. They will whine. They will fake their own death to avoid eating it. Even though they loved it YESTERDAY and begged for it today.
There you have it, Mr. Franklin. I believe you stand corrected. There are a few more certainties to life than simply death and taxes. Now wipe that smirk off your face.