It will be observed that in addition to the powers given to Justices for the punishment of offences against the peace, express authority was also conferred upon them by the same instrument for the prevention of such offences, for they were specially ordered to "take sufficient surety and mainprise of all them that be not of good fame." We have seen how under the decennary or tything system, all freemen were bound to find sureties for the preservation of the peace, and we have watched the decay of that system after the Norman invasion; in the provisions of this Act of Parliament, however, we may discover at least a partial revival of the ancient plan of demanding guarantees against any contingent infraction of the public peace, and of associating in a joint pecuniary responsibility the actual or potential peacebreaker with his immediate neighbours.[50] The "sufficient security" which Justices were authorised to take might be of two kinds--"Surety of the Good Behaviour" and "Surety of the Peace," and the security might be by Bail or by Mainprise, the difference between the two being "that mainpernors are only surety, but bail is a custody; and therefore the bail may retake the prisoner, if they doubt he may fly, and detain him."[51] ... Sureties of the Good Behaviour and Sureties of the Peace were granted on suspicion or on the flimsiest sort of evidence; for instance, "any suspected person who lives idly, and yet fares well, or is well apparelled, having nothing whereon to live," any common gamester, or the reputed father of a bastard child, or an eaves-dropper even, might be called upon to find mainpernors or bail; and so great discretion was required on the part of the Justices, who had to decide such knotty points; it was consequently of the highest importance that these officers should be familiar with the districts in which their duties were performed, and legal erudition was a consideration subordinate to personal character and local knowledge. When the Law was young evidence was received for what it was held to be worth, without distinction as to whether it might be hearsay, circumstantial, or direct; the word of a thane would prevail against the evidence of six ceorls; in fact the credibility of every witness was appraised in proportion to his social position, just as a man's life had formerly been estimated at a distinct valuation, and scheduled according to a recognised scale.[52]