 This brought probability to the foreground. Reichenbach embraced an empirical approach to probability and maintained that probability values must be determined on the basis of experience alone. What can be extracted from experience are frequencies, and it is on their basis that probability must be fixed. Reichenbach called the method for obtaining probability values induction by enumeration. This consists in counting the relative frequency of a given attribute in the initial section of a sequence of observations and inferring that such frequency will persist approximately for the rest of the sequence when this is indefinitely prolonged. This procedure forms the content of the canon according to which the frequency interpretation prescribes fixing prior probabilities, a tenet Reichenbach called Rule of induction: