Or at the very least, if a new business isn't generally thought to be impossible.

Very true! In my own case, I like to think "impossible," because I don't want to fall into the trap of thinking that I have the insight to know the difference between actually-impossible and impossible-for-mere-mortals-to-conceive.

So if something seems impossible to me, I try to consider the possibility that the problem is my lack of imagination.

My assumption: He forgot the quotation remarks around "impossible".