  Du Châtelet distinguishes those who use hypotheses well from those who use them badly, and she recognizes a third  group—those who eschew the use of hypotheses altogether largely due to perceived misuse of them among their predecessors and contemporaries. Among those who use hypotheses poorly are those working in the Cartesian tradition and those in “the Schools” who are especially guilty of spouting unintelligible jargon (IP Avant-Propos VIII, §55). The key downfalls of those who make bad use of hypotheses are the mistakes of taking them as truth (IP §62–63), and of building theories and systems upon them that resemble “fables” and “dreams” (IP §55) more than they resemble a science of nature firmly rooted in empirical knowledge of nature. As a consequence of previous abuse of hypotheses, Du Châtelet notes that many in her own century have entirely shied away from their use—or at least claim to have done  so—which they regard as (quoting Newton) the “poison of reason and the plague of philosophy” (IP §55). Du Châtelet stresses that it is a mistake, however, to believe that hypotheses are useless in physics just because they have been abused in the past (IP §63), and she suggests that hypothetical thinking is not only useful, but indeed necessary; without hypotheses, almost no progress would have been made in astronomy (IP Avant-Propos VIII, §57), and they are also valuable in physics (IP §55). She even goes so far as to claim “without hypotheses… there would be no astronomy now” (IP §57). To bolster her case, she details a few recent successes in astronomy which relied pivotally on the use of hypotheses with theories of Copernicus (IP §57 and §67), Kepler (IP §58) and Huygens (IP §57 and §67) featured as evidence. Those who refuse to include hypothetical thinking in their scientific method are guilty of retarding the progress of science no less than are those who include such thinking but do so badly (IP §54).