Over the last couple of years, I've noticed multiple books, magazines, and web sites discuss what the most significant technology of the 20th century might be. Frequently lists are made that include such notable inventions as the computer, the television, and the airplane. Other commonly suggested inventions are air conditioning, the transistor, the microchip, the jet engine, and the photocopier. Wikipedia lists these as the most influential inventions in the 20th century: antibiotics, oral contraceptives, plastics, transistors, and the Internet.

Those are all impactful inventions, all right, but none of them deserve the Number 1 spot. It's quite clear to me what the most significant invention of the 20th century is: undo

The forerunner of "undo" technologiy was white out (for those of you too young to remember, white out allowed you make corrections to typewritten pages after the fact and was a big deal in offices prior to the desktop publishing revolution.) It was the first of a group of inventions whose collective purpose is to change things, to alter the past, to allow one to take something back and do it over again. It led to powerful ideas in computers like the backspace key on the keyboard, the Undo feature in desktop applications, transactions that can be rolled back, and backup/restore. Of course, I could go back further in time and focus on earlier devices like the eraser (1770) , or the fact that it's been a woman's prerogative to change her mind for eons, but I think white out marks a point where we took an idea and ran with it wholesale.

It's hard to imagine composing text or writing code without modern editing facilities like backspace,  undo, cut and paste. Imagine that everything you wrote had to be just right the first time you put it to paper. Yet that's how it used to be by and large.

Society has strongly embraced the notion of "second chance" in numerous ways. Judges and juries frequently hesitate to penalize offenders, searching for a reason to give someone a second chance. The sky-high divorce rate indicates how the insitution of marriage, once viewed as permanent, can now be easily undone. While credit bureaus carefully track your credit history, they only do so for 7 years back so that you can mend your behavior. Many sales contracts have a cooling off period in which you can change your mind. Like most significant inventions, white out and its progeny have given us plenty of good and bad consequences to reflect on.

P.S. I used undo heavily in composing this article, and can't fathom what it would be like to live without it.