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