One commonly hears that Quantum Mechanics refutes or disproves the principle of causality. and yet if this were the case, qm could not be used to build highly precise machines such as lasers. the truth is that qm makes of use of a modified causality. the normal causal relation is that event A necessarily determines event B in qm, this relaton gets modified such that: event A necessarily determines result B or C. thus event A necessarliy determines the the result will fall within the specified range. qm is determistic in this sense.