Abstract :
The propensity automaton is an automaton whose state itself gives the probability distribution over the outputs. This paper gives the background that has led the author to the idea of a propensity automaton and explains the differences between the propensity automaton, fuzzy automaton, and stochastic automaton. Fuzzy logic and propensity logic are compared, and it will be explained how the propensity logic becomes a nondistributive logic. This paper is not intended to be a logically tight systematic exposition, but rather a narrative, at times tutorial, explanation of the motivation of an idea.