Immediately after the lid is closed, no one knows the state in the box. This statement seems to be true. The common sense says that at some time later, the radioactive material will decay and the diabolical device will work to make the cat be doomed. This statement also sounds to be true.
The physicists want to know what is going on inside the box before someone will open the box at the end of the experiment. Before the box is opened? Of course, it is sure that the cat is either alive or dead. Is there any other option? says the common sense. But is this common sense really true? Can anyone say so without actual observation?
The point is that, the physicists want to know the state in the box without causing any effect on all of the experiment- the radioactive material, a Geiger counter, the hammer, the flusk of poisonous liquid and the cat. Can they purely observe while the experiment is being done?
According to convincing arguments and experimental evidences, any observation on a system will necessarily cause an effect on the system. Therefore, the physicists are not able to know what is happening inside the box without causing any effect on the things in the box. At the very instant they take a look into the box, the state in the box suddenly changes. That is, the very action of observation will change the state of the system under study itself instantaneously.
Thus, after all, no physicist will ever be able to know what is happening inside the box while the experiment is going on. This logic is quite strange, indeed! Or did I miss something? How should we think?