This is related to Dijkstra's suggested style of programming. He suggested, or in fact insisted that the proper way to program is to create along with each program mathematical proofs that the program will behave as expected under each possible combination of inputs. This is something that might conceivably result in bug free programs.

Needless to say this style was not adopted, and in fact a very very different style that practically guarantees a lot of bugs was used.

So the expectation that programs be perfect seems impossible now, but it was not for Dijkstra considering the style of coding he had in mind.