The doctrine which holds that when there are two opinions, one in favor of liberty and the other in favor of the law, if the latter is the more probable one, it must be followed; that is, the law must be observed, because it has stronger and higher claims than those of liberty.
Theoretically probabiliorism may be defended, but it is not of much practical value, because it ultimately leads to tutiorism, which is entirely false and untenable.
During the 17th and 18th centuries probabiliorism found much favor among moral theologians, but today it has very few advocates.
It is opposed to probabilism.
New Catholic Dictionary