Inductive reasoning is one of the many battlefields for conflicting philo- sophical opinions, and one that is still relatively lively today. The reader
who went through Vol. I of this work has had a good opportunity to notice
two things. First, inductive and analogical reasoning playa major role in
mathematical discovery. Second, both inductive and analogical reasoning
are particular cases of plausible reasoning. It seems to me more philo-
sophical to consider the general idea of plausible reasoning instead of its
isolated particular cases. The present Vol. II attempts to fonnulate certain
patterns of plausible reasoning, to investigate their relation to the Calculus
of Probability, and to examine in what sense they can be regarded as
"rules" of plausible reasoning. Their relation to mathematical invention
and instruction will also be briefly discussed.