Hmmm ... this one might be tricky. Here, Bohr is probably referring to quantum theory of the time, now known as the old quantum theory,[1] as opposed to modern quantum mechanics.

Translators may wish to dig into their science history books to see if there is an appropriate term for this in the target language.

[1] http://en.wikipedia.org/wiki/Old_quantum_theory

Interesting, but I doubt it makes a difference when translating.

It does if he's referring to the specific set of “heuristic prescriptions” that were applied to achieve accurate results from the classical model. Seeing how the experimental results that led to subsequent quantum theories were wholly incompatible with classical physics, it was truly shocking, indeed.

Modern quantum mechanics does present some remarkable, unintuitive results and paradoxes, but as opposed to the old quantum theory, it's self-consistent.

If, however, one takes the view that he's referring to quantum theory in general, before the theories that now fall under that term had not even been thought up, then it might be simpler to translate.

I just got to wonder and figured I'd leave a note here in case it might interest anyone or turn up some insight. I'm starting to lean a little toward the latter view, but am still on the fence about it.