i found the following proof of Bell's theorem : we measure spin in 3 different directions a b c we can note the counting of events N1=n(a+,b+,c+) N2. + + - N3. + - + N4. + - - N5. - + + N6. - + - N7. - - + We have N3+n4<=n7+n3+n4+n2 With n3+n4=p(+a,-b) N7+n3=p(-b,+c) N4+n2=p(+a,-c) It is violated by quantum mechanics but i don't see where the hypothesis of locality and reality comes into play.