Zachary N. Brooke (1952). The English Church and the Papacy: From the Conquest to the Reign of John. Cambridge University Press. p. 193. ISBN 978-0-521-36687-8.
The only explanation of him that seems to me to fit
the facts at all is that he was one of those men who,
exalting to the full the role they have to play, picture
themselves as the perfect representatives of their
office, visualising a type and making themselves the
living impersonation of it ; actors playing a part, but
Becket wanted to be the most efficient archdeacon, the best possible administrator under archbishop Theobald; he wanted to excel at falconry; later he wanted to be the best chancellor the king would ever have, as well as being the king's best friend. He would put on the grandest show when acting as diplomat on behalf of the king when sent on a mission to the court of France to negotiate a marriage between Henry and Eleanor's eldest son, the Young Henry, and Margaret, the daughter of the King of France. He was fearless when leading his own troop of knights into battle during the Toulouse campaign of 1159. It is therefore not surprising that he would want to be the most stubborn, insistent steadfast archbishop of Canterbury that there ever had been.
His personality did not change when he became archbishop. He wanted to do justice to his new position by scrupulously following ecclesiastical law to the letter, this was manifest in his support of the liberties of the church, for papal supremacy and the principles laid down in the canon law. He had warned the king not to appoint him archbishop, that he would come to regret it. The rest is history, as they say.
Rudyard Kipling in his poem If... wrote
If you can keep your head when all about you
Are losing theirs and blaming it on you,
If you can trust yourself when all men doubt you,
That was Becket, but he failed to follow through with the following
But make allowance for their doubting too;
Becket may have been suffering from a moderate form of personality disorder which made him stubbornly persistent in his cause, strive for perfection in whatever he did: obsessive-compulsive personality disorder perhaps?
Jame Craigie Robertson states in Becket, Archbishop of Canterbury. (1859) pp. 326–.
Becket stated in a letter to the pope in 1168 that the Battle Abbey case "as one in which the secular power had been wrongly exalted against the papacy (Epp Thom i 54). For in truth it would appear that Becket was quite incapable in viewing his own conduct dispassionately. He seems to have fancied that, in exchanging the chancellorship for the primacy, he had only been released from all obligations as to money, but had got rid of his former self; and thus he would be quite ready to reprobate, as if he were altogether guiltless, an act in which he had been a chief instrument.
Ed. Herbert Waddams (1970) 1170-1970, St Thomas Becket: Canterbury Cathedral Chronicle No. 65. Friends of Canterbury Cathedral
In Archbishop Thomas Becket - The Saint by David Knowles p. 5
"... we may say that it is at least debatable whether Thomas Becket was a saint when alive and a martyr in death. I will confess that, after more than twenty years of fairly close study and reflection, I am fairly certain that he was a martyr, and still doubtful whether he was a saint in life."
In David Knowles Archbishop Thomas, a Character Study p. 13
David Knowles said that Becket's personality changed during the course of the conflict. The decisive moment of his break with the world and the past, Knowles said, occurred at Northampton, in October 1164 when Becket's confessor advised him, "The affair is no longer in your hands but God's, and He will be with you. Stand fast in your just cause." Thereafter, Knowles wrote Becket " carried his cross with a realization of its power and of its message."
As I see it Becket had an inferiority complex. He thought he was below anyone in authority above him and all those whom he served, and he thought and knew he was above all those who owed him fealty and homage. He served whomsoever he was subordinate to in an extraordinary manner. He knew his place. He was obsequious. He was undoubtedly extremely gifted in the service of others. He used his skills to serve whomsoever he owed fealty and homage to: he served that person to his utmost skill. Whosoever it was they were always amazed with the job he did for them, whether that was Osbert Huit-Deniers, Archbishop Theobald of Bec, King Henry II as Chancellor, the Pope and God as Archbishop of Canterbury, and finally God as Saint. However serving both the King and God at the same time proved contradictory. To resolve this contradiction he chose God.
One might seek to understand or speculate where Becket learnt to respect the notion of hierarchy so noticeably. The church had hierarchy. The kingdom was also feudal in structure. Hierarchy abounded everywhere. At an early age Becket was sent to boarding school [Merton Priory]. The notion of hierarchy would almost certainly been enforced upon him in that environment. When he joined archbishop Theobald's court, clearly, Roger Pont de l'Eveque, later to become archbishop of York, thought of Becket as his subordinate or as a jumped up junior, enough to want to bully him. Hierarchy was of an everyday occurrence in environments like this - learn to respect and obey your betters and those set above you.
Inferiority complex - Wikipedia
Zachary N. Brooke (1952). The English Church and the Papacy: From the Conquest to the Reign of John. Cambridge University Press. ISBN 978-0-521-36687-8.
thomas of london. Chapter 9 Character of Thomas of London: CUP Archive. pp. 225–.
British Historical Documents: Life of Thomas Becket (Gervase of Canterbury) 1853
The London Magazine, Or, Gentleman's Monthly Intelligencer. Character of the Famous Thomas Becket: R. Baldwin. 1767. pp. 393–.
Richard Hurrell Froude; James Bowling Mozley (1839). Remains of the Late Reverend Richard Hurrell Froude: v. 2. J. G. & F. Rivington. pp. 561–.
John Gillingham (1 January 2005). "Hanna Vollrath: Was Thomas Becket Chaste?". Proceedings of the Battle Conference 2004. Boydell Press. pp. 198–. ISBN 978-1-84383-132-7.
Gesine Opitz-Trotman (2010). "Birds, Beast and Becket ...". God's Bounty?: The Churches and the Natural World. Boydell & Brewer. pp. 78–. ISBN 978-0-9546809-6-1.
Frank Barlow (1990). Thomas Becket. University of California Press. pp. 55–6. ISBN 978-0-520-07175-9.
Personality disorder - Wikipedia
Obsessive–compulsive personality disorder - Wikipedia
Character and Habits of Thomas Becket
Character and Habits of Thomas Becket