Leonard Mlodinow’s three laws of probability:
1. The probability that two events will both occur can never be greater than the probability that each will occur individually.
2. If two possible events, A and B, are independent, then the probability that both A and B will occur is equal to the product of their individual probabilities.
3. If an event can have a number of different and distinct possible outcomes, A, B, C, and so on, then the probability that either A or B will occur is equal to the sum of the individual probabilities of A and B, and the sum of the probabilities of all the possible outcomes (A, B, C, and so on) is 1 (that is, 100 percent).