Here is a counter-example to the general validity of the "it was all right in the past" argument. Think about the iteration x_n+1 = a * x_n * (1 - x_n) Usuall

Here is a counter-example to the general validity of the "it was all right in the past" argument. Think about the iteration x_n+1 = a * x_n * (1 - x_n) Usually one rushes to examine a > 2, where there are interesting phenomena of bifurcation, period doubling, and chaos. Go back and look at a < 2. The iteration converges and defines a function f(a). It is a rather strange function. For 0<a<1 f(a)=0. Then for 1<a<2, f(a)>0. Imagine if this were some kind of theory of technological unemployment, with the parameter a being the level of technology. Technology grows and grows 0.2, 0.5, 0.9, without any problem of technological unemployment, but there is a threshold at a=1, and boom! at a = 1.1 there is lots of technological unemployment. The most general argument, that technology didn't lead to unemployment in the past, so it will not do so in future, is at heart a claim that functions like f never arise naturally. But clearly they do! On the other hand, showing that an argument is invalid doesn't help with working out whether the conclusion is true. Indeed, the counter example also serves as a challenge to believers in technological unemployment. There are toy models in which things are zero for a good while, then a threshold is crossed and things start to happen. Is there any model of technological unemployment with a threshold arising naturally out of the dynamics?