So, four guys are sitting down, having coffee. The men, in their conversing, eventually came to be discussing the greatest invention of all time.

One man claimed, "It was the airplane. There has never been such a convenient way to get hundreds of thousands of people across the oceans daily."

A second man postulated, "I think it would be the lightbulb, for without it, we could not efficiently work in the dark."

A third man stated, "The greatest invention was the wheel. Without it, we never would have been able to move big, heavy objects to create some of the greatest wonders of the world."

The fourth man contemplated his answer for a moment. Eventually, he came to a decision: "The greatest invention is the thermas!"

"The thermas?" the other three replied.

"Well, in the winter, you put hot coffee in it, and it keeps it hot. In the summer, you put cold water in it, and it keeps it cold."

The other men were baffled at how the thermas could compare to these other truly grand inventions.

Upon further questioning, the fourth man reiterrated, "It keeps cold water cold, and it keeps hot water hot. I mean, how does it know?"

(If you think of something not on the list, add it below.)

ChiXX0rz.

Fire. Thre greatest invention of all time. From which all other inventions sprung. No other single invention has had as much impact on human civilization, society, evolution, or psyche than fire.

Indoor Plumbing. The second greatest invention of all time. Without plumbing cities could never has grown as large as they have, the concentration of human resources that have allowed us to ascend to our current level would have never been reached.

Soap. The third greatest invention of all time. Proper sanitation save millions of lives each year.

fire doesnt count there, coyote, its not an invention. its a state of matter. however, I suppose the harnesing of said matter IS an invention. or the cration. I agree with the sanitation thing though!

Overall, I'd say the greatest invention/discovery would be those inventions/discoveries associated the the forging of metal.

Without that, we'd still be farmers/nomads.

Recently though, I'd have to say the transistor - it allows most of all of the neato stuff today, and it's not even a hundred years old yet.

Humans; the natural resistor! ^_^

"Fire" was a discovery. For the purposes here, "invention" refers to a man-made object.

'nother good canditate would be rope and weaving.

Allowed sailing, paper, woven cloth, the pulley, etc etc.