THE ordeal of public scrutiny ended this week for Clarence Thomas. The substance of his answers was not always what inquiring senators - or the listening public - might have liked. But without a doubt Americans got a feel for a man almost sure to occupy a seat on the nation's highest court.The impressions of intellectual ability and self-command are strong. Judge Thomas clearly grasps the gravity of judicial work and its demands for open-mindedness and fairness. He promised to take these qualities of thought with him to the Supreme Court. We see no reason to doubt his sincerity. The doubts that surfaced during the hearings revolved around the nominee's disavowal of earlier positions. In the past, for example, he has been a sharp critic of affirmative-action policies, of some aspects of the federal voting-rights law, and of the Supreme Court's decision upholding Congress's right to appoint special prosecutors. On one occasion he seemed inclined toward a "natural law" approach to banning abortion. Were these the intentionally provocative statements of someone trying to enliven the capital's policy debates, as the judge seemed to imply, or enduring attitudes? We hope that the judge has changed his mind - and that such shifts will be accelerated by the extraordinarily hard thinking demanded of a Supreme Court justice. Clarence Thomas brings a unique background to the court. He should be sensitive, as few justices before him could have been, to the challenges facing the disadvantaged in America. He said things during the hearing that indicated his code of individualism doesn't exclude empathy for those who haven't been able to grasp their bootstraps. He also showed welcome concern about the erosion of such fundamental rights as the free exercise of religion. If he is confirmed by the full Senate, as seems likely, the Supreme Court's docket will give Thomas ample opportunity to prove that his words over the past week do indeed have substance.