Shortly afterwards, on 1 Dec, the archbishop arrived at Sandwich (for particulars of John's return, and the events which followed down to near the middle of December, see his letter to Peter of La Celle, epist. ccc. pp. 240-5).
On the fatal 29 Dec. John was in the archbishop's company at Canterbury when his murderers made their appearance, and the words which passed between him and Thomas before they went into the church are recorded (Benedict of Peterborough, Pass. S. Thom. in Robertson's Materials, ii. 9; William FitzStephen, Vit. S. Thorn., ib. iii. 134; Auct. anon. I., Vit. S. Thom., ib. iv. 74). John's counsels of prudence were disregarded by the archbishop, and he went with the rest into the cathedral. But when the actual attack began his courage forsook him. William FitzStephen, who with Edward Grim and Robert, canon of Merton, remained on the spot, asserts (ib. iii. 139) that John and all the other clerks fled and took refuge under altars or where they could (cf. Herbert of Bosham, Vit. S. Thom., ib. iii. 491). William Tracy, indeed, boasted that he broke John's arm, but the blow really struck Edward Grim, and then descended upon the archbishop's head (William of Canterbury, Vit. S. Thom., ib. i. 134; cf. William FitzStephen, ib. iii. 141, Herbert of Bosham, ib. iii. 498). Still, it is possible that Tracy was not wholly mistaken, and that John, in fact, returned to the scene of the fray. Certainly, he was believed to have been 'pretioso sanguine b. m. Thomas intinctus' (Peter Of La Celle, epist. cxvii., Migne, ccii. 567).
For the rest of John's biography materials are scanty, few of his letters having been preserved. Immediately after the archbishop's death he urged the inclusion of his name in the calendar of martyrs (epistt. ccciv., cccvi. pp. 258, 263), and wrote a life of him in the style of a hagiologer, with a view to securing his canonisation. Part of this work is substantially a transcript of epist. ccciv. pp. 252 ff. Afterwards he was active in promoting the acceptance of Richard, prior of Dover, as archbishop; and he seems to have remained under him at Canterbury. Meanwhile he received church preferment, and in 1174 is named as treasurer of Exeter Cathedral (Le Neve, Fasti, ed. Hardy, i. 414; cf. Chron. Monast. de Bello, a. 1176, p. 172, 1846). Two years later he was raised to the bishopric of Chartres. The appointment was made by the advice of his old friend Archbishop William of Sens, and partly out of regard for his trusty attachment to St. Thomas (see the letter of Louis VII, printed among John's letters, epist. cccxxiii. p. 291). The chapter elected John unanimously on 22 July 1176 (Gall. Christ, viii. 1146, 1744), and sent over the dean, precentor, and chancellor to announce their choice (epist. cccxxiv. p. 292). On 8 Aug. he was consecrated at Sens (Gall. Christ. 1. c.) He chose always to style himself bishop 'divina dignatione et meritis S. Thomæ martyris.' What is known of his official acts is recorded in 'Gallia Christiana,' viii. 1147 f. Almost his earliest exercise of power was to excommunicate no less a person than the Count of Vendôme, for injuries he had inflicted upon the monastery of the Holy Trinity at Vendôme. He did not release him until 1180, when he promised to make restitution (epist. cccxxvi. pp. 294 f.; cf. Recueil des Historiens, xii. 488 n. b, 1781). On 21 Sept, 1177 the bishop was present at the solemn meeting of the English and French kings, when peace was made, near Ivry (Gest. Henr. II, ed. Stubbs, 1867, i. 194), and in March 1179 he attended the third Lateran council (Mansi, Concil. Collect. ampliss. xxii. 239, 464, 1778), and took an active part in its proceedings (pp. 303, 318, 378, 434 f.) In the following year, on 25 Oct., he died, and was buried in the monastery of Josaphat, near his city. He bequeathed to his own church most of his possessions, reliques (including a phial containing some of the blood of St, Thomas), and books. It is said that his entire library thus passed to the cathedral, but by the middle of last century most of the books had been lost (Gall. Christ. viii. 1148 f.) John was succeeded in his see by the friend of his whole life, Peter of La Celle.
John of Salisbury, 'for thirty years ... the central figure of English learning' (Stubbs, Lectures, p. 139), was the fullest representative of the best scholarly training which France had to give, and he had used his time, constantly occupied as he was by other cares, to such signal profit that no writer in the middle ages can be placed beside him in the extent and depth of his classical reading. It is this fact, perhaps, which gives his works their unique attraction. John was a humanist, with the tastes and the quick curiosity of a humanist. If his knowledge of Greek was hardly more than what could be picked up from glossbooks, there is still good ground for believing that he was able to increase the store of accessible Greek literature by employing a Greek of Italy to translate the later books of Aristotle's 'Organon,' the 'Analytics,' 'Topics,' and 'Sophistici Elenchi' (see Schaarschmidt, pp. 120 f.) The disciple of Abailard, he divined a middle course between the accepted tenets of realism and the theological perils which lay beneath the qualified