[continued from previous message]   
      
   spatiotemporal structure of human sensory experience, and are therefore   
   unlikely to be applicable to what is inaccessible to human sensory   
   experience. While measurement outcomes and the experimental conditions   
   under which they are obtained are directly accessible to human sensory   
   experience, what happens between measurements is not, and therefore   
   cannot be expected to be expressible with the concepts at our disposal.   
      
   The second measurement problem, sometimes referred to as the “small”   
   one, is the question why certain projection operators |x⟩⟨x| (or the   
   subspaces into which they project) represent possible measurement   
   outcomes, while others do not.   
      
   The reason we never experience a measurement pointer as simultaneously   
   pointing in two different directions is that measurement outcomes are   
   experiences, and experiences conform to Kant’s principle of   
   thoroughgoing determination. Assuming that every thing was accessible to   
   direct sensory experience, Kant9 concluded that   
      
        every thing, as to its possibility, stands under the principle of   
   thoroughgoing determination, according to which, among all possible   
   predicates of things, insofar as they are compared with their opposites,   
   one must apply to it.   
      
   Because Kant’s principle applies to everything that is accessible to   
   sensory experience, it applies to every outcome-indicating property, and   
   therefore it implies the definiteness of every measurement outcome.   
      
   As long as the cat is directly accessible to sensory experience, it can   
   serve as a measurement pointer: if after an hour the cat is alive, it   
   indicates that as yet no atom has decayed, and if after an hour the cat   
   is dead, it indicates that at least one atom has decayed. Is it possible   
   to make the cat inaccessible to direct sensory experience by, say,   
   penning it up in a steel chamber? Suppose that it is. While we are then   
   ignorant of the state of the cat (alive or dead), we are by no means   
   cognizant of the cat’s being neither dead nor alive. To be cognizant of   
   such a state, we must have evidence that such a state obtains. Is it   
   possible to have such evidence?   
      
   Let’s start with the simplest possible situation. It is perfectly   
   feasible to prepare a particle in such a way that its spin, if measured   
   with respect to the vertical axis, is certain to be found up, and that   
   its spin is equally likely to be found up or down if measured with   
   respect to a horizontal axis. In this case, finding the spin up with   
   respect to the vertical axis implies that the spin is neither up nor   
   down with respect to any horizontal axis. It is also possible (if   
   technically more challenging) to perform an experiment that has a   
   possible outcome which implies that neither of the following is the   
   case: no atom has decayed and at least one atom has decayed. And it   
   would also be possible to obtain evidence that the cat is neither alive   
   nor dead if it were possible to perform an experiment that has a   
   possible outcome which implies that the cat is neither alive nor dead.   
      
   Let us furthermore take into account that the properties of quantum   
   systems are contextual:10 they are defined by the experimental   
   conditions under which they are observed, and they only exist if their   
   presence is indicated. Since presently we are treating the cat as a   
   quantum system, we need to ask: is it possible to conceive of   
   experimental conditions that define a property whose existence would, if   
   indicated, imply that the cat is neither alive nor dead?   
      
   Let’s take the craziness a step further. If such experimental conditions   
   could be created, it would be possible to transform a living cat into   
   one which is neither dead not alive. It would then also be possible to   
   transform a dead cat into one which is neither dead nor alive. And it   
   would then be possible to determine, by a subsequent measurement,   
   whether the cat is dead or alive, and it would be possible to find that   
   the cat is alive. In other words, it would be possible to resurrect a   
   dead cat. I am not making this up. Luigi Picasso, for one, writes in his   
   Lectures in Quantum Mechanics (Springer, 2016, p. 341) that “tomorrow,   
   when the observables that today do not exist will become available, we   
   will be able, by means of two measurements, to resurrect dead cats...”   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)