The first stage of the transition from the traditional view to the modem view of uncertainty began in the late 19th century, when physics became concerned with processes at the molecular level. Fuzzy sets and fuzzy logic (1995)
To select an appropriate fuzzy implication for approximate reasoning under each particular situation is a difficult problem. Although some theoretically supported guidelines are now available for some situations, we are still far from a general solution to this problem. Fuzzy sets and fuzzy logic (1995)
Probability theory is an ideal tool for formalizing uncertainty in situations where class frequencies are known or where evidence is based on outcomes of a sufficiently long series of independent random experiments. Possibility theory, on the other hand, is ideal for formalizing incomplete information expressed in terms of fuzzy propositions. Fuzzy sets and fuzzy logic (1995)