(1.) _The so-called strength of a motive is the degree of probability that the will will act in accordance with or on account of it._ "And it is most important to remark that the _result_ is not always, nor in most cases, necessarily as the _highest probability_. The will may choose for the higher or for the lower. And as the will may choose for a lower rather than a higher probability, so the will may choose on account of what is called antecedently a _weaker_ over a _stronger_ motive. And hereby is once for all established the difference between mechanical force and motive influence--that whereas in the former, by necessity, the greater effect results from the greater force, in the latter the less is possible from the greater, the greater from the less."[542] That result is not as the highest probability Dr. Whedon has shown most conclusively from the doctrine of Contingencies or Probabilities. And on this he grounds his doctrine of _contingent motive probability_. "This contingent character of motive influence is correspondent with the alternative character of that which is its sole possible object--will. An alternative will and a contingent motive influence are correlatives. They mutually explain and sustain each other. To admit either is to admit both. And so a unipotent will and a necessary motive influence are correlatives. He who is compelled to admit one is compelled to admit the other. It will be a mere controversy about a word to say that an influence which does not produce effect is no influence. That may legitimately be called an influence, it is important to add, which is conceived as _possessing an intrinsic probability for result, though the higher probability be a contingency_ for which there exists power of _failure_. If so, then the doctrine of contingent motive influence is established, and the doctrine of volitional necessity is at an end. The relation between physical force and effect is _necessity_. The relation between motive and volition is _contingency_."[543]