The truth-functions can be ordered in series. That is the foundation of the theory of probability. 5.101 5.11    If the truth-grounds which are common to a number of propositions are all also truth-grounds of some one proposition, we say that the truth of this proposition follows from the truth of those propositions. 5.12 (4)  In particular the truth of a proposition "p" follows from that of a proposition "q", if all the truth-grounds of the second are truth-grounds of the first. 5.13 (6)  That the truth of one proposition follows from the truth of other propositions, we perceive from the structure of the propositions. 5.14 (3)  If a proposition follows from another, then the latter says more than the former, the former less than the latter. 5.15 (6)  If Vr is the number of the truth-grounds of the proposition "r", Vrs the number of those truth-grounds of the proposition "s" which are at the same time truth-grounds of "r", then we call the ratio   Vrs : Vr the measure of the probability which the proposition "r" gives to the proposition "s".