OPINION OF THE COURT
Dillon, P. J.Counsel for the New York State Public Employment Relations Board (PERB) charged that petitioner “caused, instigated, encouraged, condoned and engaged in a strike” against the Niagara Frontier Transit Metro System, Inc. (NFT Metro) on December 14 and 15, 1978 (see Civil *106Service Law, § 210, subd 1). Following a hearing upon which the hearing officer recommended that the charge be dismissed, PERB, rejecting that recommendation, agreed that petitioner had not caused or instigated the strike but determined that the evidence was sufficient to establish that petitioner had “condoned” the strike.
The issue to be resolved is whether PERB’s determination, on review of the entire record, is supported by substantial evidence (CPLR 7803, subd 4). The issue is one of law to be decided by the courts (Matter of Clark v Board of Zoning Appeals of Town of Hempstead, 301 NY 86, 90-91, cert den 340 US 933). In that regard, we exercise “a genuine judicial function” and are not to “confirm a determination simply because it was made by such an agency” (300 Gramatan Ave. Assoc. v State Div. of Human Rights, 45 NY2d 176, 181). The evidence upon which the determination is based must be “ [m] arked by its substance”; its substantiality “does not rise from bare surmise, conjecture, speculation or rumor” (300 Gramatan Ave. Assoc. v State Div. of Human Rights, supra, p 180). “[Substantial evidence consists of proof within the whole record of such quality and quantity as to generate conviction in and persuade a fair and detached fact finder that, from that proof as a premise, a conclusion or ultimate fact may be extracted reasonably—probatively and logically” (300 Gramatan Ave. Assoc. v State Div. of Human Rights, supra, p 181). The agency determination will not be upheld unless the record as a whole provides a rational basis to support the findings of fact upon which it is based (Matter of Pell v Board of Educ., 34 NY2d 222). Application of those principles requires that PERB’s determination be annulled.
Initially, it should be observed that in presenting evidence at the hearing, counsel for PERB relied upon a presumption, since judicially disavowed (Matter of Police Benevolent Assn. of City of Yonkers v New York State Public Employment Relations Bd., 51 NY2d 779) that a union has consented to a strike where a vast majority of its members participate in it (see Matter of Police Benevolent Assn. of City of Yonkers, 11 PERB 3168 [No. 3104]). He presented only two witnesses; Jack Heinen, in charge of payroll and auditing at NFT Metro, and Roy Klager, NFT Metro’s *107personnel manager. Neither had any personal knowledge of the conduct or activities of union leaders during the day and a half of the work stoppage.
At the close of the charging parties’ evidence, the hearing officer reserved decision on petitioner’s motion to dismiss. Thereupon, petitioner produced seven executive board members, including its president, who testified about events preceding the strike and who individually recounted their activities during the course thereof. The inescapable conclusion to be drawn from the evidence thus adduced is that the executive board members, confronted with unauthorized action by the union members, acted responsibly, consistent with their mandate as union leaders, in facilitating prompt termination of the unauthorized strike. Put another way, it is irrefutable that the executive board members made “good faith efforts to terminate the strike” (Civil Service Law, § 210, subd 3, par [e]). Significantly, though concededly not determinative, that view is consistent with the hearing officer’s affirmative findings upon which she recommended that the charge be dismissed.
It was conclusively demonstrated at the hearing that petitioner’s executive board, prior to the work stoppage, had twice recommended membership approval of tentative collective bargaining agreements with NFT Metro. These recommendations were made at meetings on August 2,1978 and December 12, 1978, and at those and other meetings, petitioner’s president, confronted by a militant minority of members who were vocally advocating a work stoppage, consistently ruled such discussions out of order, refused to entertain any motion for such job action and repeatedly stressed that the executive board disapproved of any work stoppage.
When the strike began on the early morning of December 14 petitioner’s president assured NFT Metro’s executive vice-president that the union was not responsible for the work stoppage and that the union “would do everything that was possible to keep the busses rolling”. He explained that the “trouble” was being caused by a “few people”. Indeed the only fair inference to be drawn from the record is that a vast number of union members did not favor or *108support the work stoppage. Many uniformed bus drivers reported for work on the early morning of December 14 only to be confronted by picket lines which had been established without union authorization.
Since it is universally agreed that no evidence was presented at the hearing to support the charge that petitioner “caused” or “instigated” the strike, we need only review PERB’s determination that petitioner “condoned” the strike. It is premised upon three findings:
(1) That the “unauthorized absence” of executive board members from their work assignments provided “an example for the rank and file members” who followed it.
(2) That the strike ended “pursuant to a vote of [petitioner’s] leaders and their direction to the employees to return to work”, thus demonstrating that the executive board members had “control of the situation” and could have earlier terminated the strike.
(3) That the executive board members failed “to exert any significant forceful efforts to terminate the strike before receipt of the restraining order”.
None of those findings has a basis in the record. As to the first, the evidence presented, not by the charging party but by petitioner, fully accounts for the activities of the executive board members during the period of the work stoppage. David Mulready reported for work at NFT Metro’s Niagara Falls Station at approximately 4:15 a.m. on December 14, as did several other bus drivers, who took their buses out on assigned routes. He remained at the station throughout the day, taking phone calls from other employees who were complaining of harassment and threats. He encouraged them to continue working. Three other executive board members, Peter Zoldowski, Frank Sparacino and Daniel Reidy were excused from reporting for regular work because they were engaged in sign-up activities.* Thus they would not have reported for regular work assignment even if there had been no work stoppage. A fifth executive *109board member, Jimmy Williford, reported for work and punched in. He encouraged other employees to undertake their work assignments, and some did. Williford’s time card was punched out by Don Green, representing management, because Williford acknowledged that he was talking on the telephone to petitioner’s president. Williford then left work and went to union headquarters. Another executive board member, Edward Bernat, reported for work at NFT Metro’s offices and obtained permission to leave work at 10:80 a.m. because of illness. Bernat represented office workers who did not engage in the strike. Two other members of the executive board, Joseph Beyea and Richard Meinke, reported for work respectively at the Frontier and Cold Springs Stations but found that both premises were locked. Their testimony in that regard is supported by that of other witnesses and stands wholly unrebutted in the record. In any event a finding that Beyea and Meinke were absent from their workplace without authorization can hardly be characterized as an “example” to the membership to strike in view of the other uncontroverted evidence that the two spent the balance of the day encouraging union members to return to work. Finally, on this point, no evidence was presented by the charging party to offset the testimony of other executive board members recounting their respective efforts in exhorting union members to return to work.
Similarly, there is no evidence in the record to support PERB’s finding that the executive board members had “control of the situation” because the members returned to work upon their order. The truth is that the strike ended when the union leaders informed the membership that the latter were ordered back to work by a restraining order enforceable by imprisonment (see Civil Service Law, § 211; Judiciary Law, §§ 750, 751).
Lastly, PERB’s faulting of petitioner for having failed to exert “significant forceful efforts to terminate the strike before receipt of the restraining order” may only be said to equate petitioner’s failure to end the strike with having condoned it. The record fully supports the hearing officer’s recitation of the efforts of the members of the executive *110board to terminate the strike. They included public statements condemning the strike made to the media; visits to the various work sites encouraging union members to return to work; holding themselves specially available for service of the temporary restraining order in order to use it as a lever to force the members to return to work; and promptly disseminating word that the restraining order had been served.
Although the dissenters would wholly ignore the findings of the hearing officer, she alone had the opportunity for personal observation of the witnesses. After an assessment of the credibility of the testimony of the members of the executive board, and upon a comprehensive review and analysis of that testimony, she concluded that petitioner “should not be held responsible at all for the wildcat strike”. The evidence supportive of that conclusion stands wholly unrebutted.
In support of her finding that petitioners made good faith efforts to terminate the illegal work stoppage, the hearing officer wrote:
“The President of the [petitioner], upon being advised by the Executive Vice-President of NFT-Metro in the early morning hours of December 14,1978 that there was trouble at the locations, urged management to remove the pickets and parked cars so that the men could report to work. He then called an Executive Board member to check the locations and report back to him. This was the first indication he received that some type of job action or work stoppage was taking place. When members of the Executive Board called the President later in the morning to indicate that there were picket lines at some of the locations, they were instructed ‘to do whatever was possible to get the buses rolling’. The President then reported to [petitioner’s] headquarters and, with several Executive Board members, went to the locations to try to talk the men into going back to work for the rest of the day. It was the President’s testimony that after visiting the locations and speaking to the men, that they would not cross the picket lines for fear, in part, for their physical safety. Based upon prior discussion with management representatives of NFT-Metro, the Presi*111dent was aware that they were seeking a court injunction and he expected, that when he had the document in hand, that he could persuade the men to return to work. On the evening of December 14, 1978, the President was interviewed on television and stated that the work stoppage was unauthorized and that the men should be back working.
“Having been advised that the injunction was secured late in the evening of December 14, the President directed that all representatives of the [petitioner] should be available for service of the injunction. When, on December 15, the [petitioner’s] officials received the injunction, they promptly went to the work locations, instructed the men that they were now required by the court to return to work, and they did.”
Not only are the hearing officer’s findings fully supported in the record but PERB’s determination that petitioner condoned the strike is wholly irrational. Its decision to reject the hearing officer’s recommendation appears to be premised upon a judgment that the union could have done more to end the strike in less than the day and a half of its duration. Such speculation, viewed in the context of the whole hearing record, does not rise to the level of “substantial evidence” to support its determination. The danger inherent in its decision on these facts is that a union, despite the best efforts of its leadership, may be held guilty of a violation of section 210 of the Civil Service Law whenever a wildcat strike occurs.
The petition should be granted and the determination annulled.
When one is engaged in sign-up activities he does not report for regular work assignment, but appears at his assigned work location to receive employee requests for bus route assignments which are then made based on employee seniority.