III
  We conclude by briefly addressing what appear to be two underlying
concerns of the parties and amici in this case. Respondent expresses
apprehension that abandonment of -general acceptance- as the exclusive
requirement for admission will result in a -free-for-all- in which
befuddled juries are confounded by absurd and irrational
pseudoscientific assertions.  In this regard respondent seems to us to
be overly pessimistic about the capabilities of the jury, and of the
adversary system generally. Vigorous cross-examination, presentation
of contrary evidence, and careful instruction on the burden of proof
are the traditional and appropriate means of attacking shaky but
admissible evidence.  See Rock v. Arkansas, 483 U. S. 44, 61 (1987).
Additionally, in the event the trial court concludes that the
scintilla of evidence presented supporting a position is insufficient
to allow a reasonable juror to conclude that the position more likely
than not is true, the court remains free to direct a judgment, Fed.
Rule Civ. Proc. 50 (a), and likewise to grant summary judgment, Fed.
Rule Civ. Proc. 56.  Cf., e.g., Turpin v. Merrell Dow Pharmaceuticals,
Inc., 959 F. 2d 1349 (CA6) (holding that scientific evidence that
provided foundation for expert testimony, viewed in the light most
favorable to plaintiffs, was not sufficient to allow a jury to find it
more probable than not that defendant caused plaintiff's injury),
cert. denied, 506 U. S. ___ (1992); Brock v. Merrell Dow
Pharmaceuticals, Inc., 874 F. 2d 307 (CA5 1989) (reversing judgment
entered on jury verdict for plaintiffs because evidence regarding
causation was insufficient), modified, 884 F. 2d 166 (CA5 1989), cert.
denied, 494 U. S. 1046 (1990); Green 680-681.  These conventional
devices, rather than wholesale exclusion under an uncompromising -
general acceptance-test, are the appropriate safeguards where the
basis of scientific testimony meets the standards of Rule 702.
  Petitioners and, to a greater extent, their amici exhibit a
different concern.  They suggest that recognition of a screening role
for the judge that allows for the exclusion of -invalid-evidence will
sanction a stifling and repressive scientific orthodoxy and will be
inimical to the search for truth.  See, e.g., Brief for Ronald Bayer
et al. as Amici Curiae.  It is true that open debate is an essential
part of both legal and scientific analyses.  Yet there are important
differences between the quest for truth in the court-room and the
quest for truth in the laboratory.  Scientific conclusions are subject
to perpetual revision.  Law, on the other hand, must resolve disputes
finally and quickly.  The scientific project is advanced by broad and
wide-ranging consideration of a multitude of hypotheses, for those
that are incorrect will eventually be shown to be so, and that in
itself is an advance.  Conjectures that are probably wrong are of
little use, however, in the project of reaching a quick, final, and
binding legal judgment-often of great consequence-about a particular
set of events in the past.  We recognize that in practice, a
gatekeeping role for the judge, no matter how flexible, inevitably on
occasion will prevent the jury from learning of authentic insights and
innovations.  That, nevertheless, is the balance that is struck by
Rules of Evidence designed not for the exhaustive search for cosmic
understanding but for the particularized resolution of legal disputes.
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