In the beginning, shaving was a scary process men did daily..
with the straight or "cut throat" razor. Disaster was just a slip
away but we did it anyway.
Best left to a barber who was trained in those days to be a barber
(not a hairdresser), he could give you such a close shave with that
razor which he knew how to keep (ahem!) razor sharp with sharpening
and stropping with a leather belt.
Then the Safety Razor was invented and we breathed a sigh of
relief. Bleary-eyed, we could shave relatively safely without
slitting our own throats in the mornings. 
All we needed to do was to buy the disposable blades and we could
have a safe close shave without going to the barber.
Then Gillette appeared and decided that if 1 was good, 2 was
better. On the Trac II, the first "twin blade" razor appeared and
sparked off an arms race in shaving which is still being fought
today.
The premise is the "hysteresis" thing which your hair follicle is
gently tugged out by the first blade and is cut by the 2nd before
it slides back in, ensuring a clean shave. Sounds like BS to me but
no one could disprove it.
Other razor manufacturers started copying Gillette so hey, if it
worked the first time, it'll work again... Three is better than
Two!
So the Mach 3 was born!
Schick caught on to Gillette and decided, hey! we can play at this
game too! We'll add ANOTHER blade to it and see what happens.
The result: a silly-looking 4-bladed razor which some say shaves
really well.
Gillette must have had convulsions. So they did this...
THE FUSION!!! Five... count them.. FIVE blades on a razor's shaving
face!! Even comes with a battery operated version (why, I don't
even want to know). There's even a 6th blade on the back "for
precision shaving".
This typical dude is thinking.. what next? This???
