[credit_guy]

That is true. What should we conclude from this statement?

[JohnMakin]

That you shouldn’t assume just because in the past ideas have existed that became reality, that all current ideas are feasible or possible?

[credit_guy]

I didn’t assume that. The author makes the opposite assumption: that because nobody has ever proposed a path to technological feasibility, that thing will forever be technologically unfeasible. I simply find this argument to be very weak.