* Think about the things which are practically possible from now on.

* Think about what you want.

These people are called visionaries. Let me give an example the way I see it. Edison. Imagine the same physical situation as light bulb. You have a heat source which continuously produces heat. The heat is lost primarily due to heat radiation. The rate of loss of heat from the source is proportional to temperature to the power four. When ever you have loss with positive power, you are sure about a stable steady state (we can do some math here).

So, there exists a steady temperature for a given length of the source and given surroundings (essentially emissivity). And Edison has to find a metal/conductor whose melting point is above that of the steady state temperature.

Math tells you it is possible if you find the metal. But won't tell you whether it is possible to find that metal. No clue.. where to go..

May be I have missunderstood the term vision. But there is more to life than simple possibilities and probabilities..