Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. An enthymeme in its modern sense, is an informally stated syllogism with an unstated assumption that must be true for the premises to lead to the conclusion. In an enthymeme, part of the argument is missing because it is assumed. In a broader usage, the term "enthymeme" is sometimes used to describe an incomplete argument of forms other than the syllogism or a less-than-100% argument. For Aristotle, who defined it in his Rhetoric, an enthymeme was a "rhetorical syllogism" which was based on probable opinions, thus distinguishing it from a scientific syllogism. It is aimed at persuasion while scientific syllogism is aimed at demonstration.