In a 1942 paper, Dirac claimed that negative energy and negative this quantity are not nonsense and are mathematically well-defined like negative money. (-5[1])For a spin-0 particle, the current of this quantity is equal to (15[2])(read slowly) h-bar over (15[2])2-m-i (15[1])times (15[1])psi-star-del-psi (15[1])minus psi-del-psi-star. Application of the WKB (-5[1])approximation to a free particle (*) wavefunction gives a (-5[1])nonzero value (10[1])to this quantity in classically (10[2]-5[1])forbidden regions. Born’s rule set the square norm of (10[1])the (10[4])wavefunction amplitude as this quantity. QBism is an interpretation (10[1])of Quantum Mechanics which uses a subjective Bayesian account of (10[1])this quantity. This quantity over all space (10[1])for a normalized wavefunction is equal (10[1])to (10[1])one. For 10 points, identify (-5[1])this quantity that gives the chance (10[1])of observing a particle in (10[1])a (10[2])particular (10[2]0[3])state. ■END■