The position of his opponents throughout his reign would seem to have rested on two assumptions. The first, that a breach, on his part, of the "contract" justified _ipso facto_ revolt on theirs;[78] the second, that their allegiance to the king was a purely feudal relation, and, as such, could be thrown off at any moment by performing the famous _diffidatio_.[79] This essential feature of continental feudalism had been rigidly excluded by the Conqueror. He had taken advantage, as is well known, of his position as an English king, to extort an allegiance from his Norman followers more absolute than he could have claimed as their feudal lord. It was to Stephen's peculiar position that was due the introduction for a time of this pernicious principle into England. We have seen it hinted at in that charter of Stephen in which he treats with Miles of Gloucester not merely as his king (_rex_), but also as his feudal lord (_dominus_). We shall find it acted on three years later (1139), when this same Miles, with his own _dominus_, the Earl of Gloucester, jointly "defy" Stephen before declaring for the Empress.[80] Passing now to the other point, the existence of a rival claim, we approach a subject of great interest, the theory of the succession to the English Crown at what may be termed the crisis of transition from the principle of election (within the royal house) to that of hereditary right according to feudal rules. For the right view on this subject, we turn, as ever, to Dr. Stubbs, who, with his usual sound judgment, writes thus of the Norman period:— "The crown then continued to be elective.... But whilst the elective principle was maintained in its fulness where it was necessary or possible to maintain it, it is quite certain that the right of inheritance, and inheritance as primogeniture, was recognized as co-ordinate.... The measures taken by Henry I. for securing the crown to his own children, whilst they prove the acceptance of the hereditary principle, prove also the importance of strengthening it by the recognition of the elective theory.[81] Mr. Freeman, though writing with a strong bias in favour of the elective theory, is fully justified in his main argument, namely, that Stephen "was no usurper in the sense in which the word is vulgarly used."[82] He urges, apparently with perfect truth, that Stephen's offence, in the eyes of his contemporaries, lay in his breaking his solemn oath, and not in his supplanting a rightful heir. And he aptly suggests that the wretchedness of his reign may have hastened the growth of that new belief in the divine right of the heir to the throne, which first appears under Henry II., and in the pages of William of Newburgh.[83]