Even after many years of episodes, we still know very little about the Doctor’s origins in an official sense. His true identity (including his name) and his past remain a mystery. What we do know, is that he attended the most prestigious of the Time Lord colleges, the Prydonian academy, along with the Master, Drax and the Rani. It is also known that the Doctor was the less able of the 4 pupils (likely due to a somewhat undisciplined, wandering mind), behavior which exasperated his former teacher, Borusa. What remains buried in the past is what occurred in the years following his graduation from the Academy, and when he is first seen in episode 1 of “An Unearthly Child”. There are several theories about the reasons behind his decision to leave his home on Gallifrey, but nothing concrete.

On more than one occasion, over the course of the series, the Doctor has stated that he became gradually and increasingly dissatisfied with the Time-Lord policies of Non-Intervention, and the somewhat stagnant and stolid nature of his race. Angered over Gallifrey’s almost tacit approval of interstellar tyranny and injustice, he stole a TARDIS from a repair bay and left his home planet, ending up on Earth in the early 1960′s.

In a recent and interesting statement (in “Last of the Time Lords”), the Doctor briefly spoke of his childhood, and how Gallifreyan children are exposed to the promise and the burden of becoming a Time-Lord at the age of eight, when they are taken from their families and enrolled in the Academy. Soon after, they are initiated, taken out into the wilderness of Gallifrey to stare into eternity through a gap in the very fabric of Space-Time called the “untempered schism”. Some children are inspired, some run away, and a few are driven mad. The Doctor admits he was among those who ran away, and says “I never stopped.”

We also know that the Doctor had a family of his own, was a father and presumably a husband. Considering that the Doctor began his adventures with his granddaughter, Susan, one would have considered this to be a sensible assumption to make. However there had always been a contingent of fans who considered the Doctor to be “above” such things because he never seemed to show any real romantic inclinations in the original series. Despite the behavior, such a conclusion was a silly one, (IMHO anyway. Why certain people seemed so hesitant to simply take the man at his word confounds me to this day.) and was finally put to rest in “The Doctor’s Daughter”. What isn’t clear is if he had this family while living on Gallifrey, or after he left.

Physiology

Like all Gallifreyans, the Doctor’s physiology is quite different from that of a human. Although human at a glance, he possesses a redundant cardiovascular system (two hearts), a respiratory bypass system, and a body temperature of 60 degrees Fahrenheit. Their bodies are highly resistant to rapid changes in atmospheric pressure and temperature, as illustrated when the Fourth Doctor survived for an indeterminate period inside a medical vacuum chamber, and the 5th Doctor withstood at least 2-3 minutes in the hard-vacuum of space during a spacewalk while wearing only an oxygen helmet and no other protection. As such, their bodily fluids must be resistant to ebulism (The boiling of blood and other fluids caused by extremely low pressures), but they likely cannot survive such an environment for too long, since the Doctor has required space-suits for extended periods in space, or in an area of extremely low atmospheric pressure (Mars for example). Gallifreyans aren’t generally harmed by simple rontgen radiation (X-Rays), and can shrug off a rad level that would quickly kill a human being. They are also resistant to other energy types as well, such as high-levels of electricity, and immune or resistant to many otherwise-lethal poisons. In short, Gallifreyans are a very hardy race.

In terms of mental acumen, the Gallifreyan brain is far more complex than the human counterpart, and gifts most of them with swift powers of deduction and analysis. Their brains are so highly ordered and efficient that they generally sleep around 60% less than human beings do in normal circumstances, and can go days without sleeping at all. They can, however, fall into a healing “coma” for several hours (sometimes days) in order to more quickly recover from severe, non-lethal injuries. When they do this, their heartbeat and respiration slow to the point where life-signs are difficult to find, and they become icy to the touch. When they awaken, they are refreshed and usually almost fully recovered.

They also have senses that allow them to feel and sense things far too subtle for our perceptions, such as planetary rotation, and various types of temporal anomalies. Time-Lords are mildly telepathic, able to read-minds and even rewrite or erase the memories of lesser species. This generally requires skin-to-skin contact, making them primarily touch-telepaths, although they are often able to detect the feelings or thoughts of more powerful telepaths without needing physical contact.

It’s likely that Gallifreyans are naturally long-lived in human terms, but that is by no means certain. Not all Gallifreyans are Time-Lords, who are gifted with the miraculous additional ability of Total Cellular Regeneration. The exact mechanisms responsible for Time-Lord regeneration is not known. It’s probably interwoven into their genetic makeup, and seems as if it may be tied into the 2nd heart all Time-Lords have (The half-human meta-crisis Doctor had only one heart, and stated he would age normally and never regenerate).

What is clear, is that as a prelude to regeneration, a restorative energy builds in the Time-Lord’s body, and will eventually erupt outwards as it restores and alters every single cell. Once the energy starts building, regeneration is inevitable unless a compatible biological receptacle is present (such as the Tenth Doctor’s original, severed right hand). In such an instance, the energy can be used to heal the body, and then expelled into the receptacle, which will prevent the total cellular change. If allowed to run its course, the process results in a new body for the formerly death-bound Time-Lord, and oft times a radical change in personality. Some Time-Lords (Such as K’Ampo, Romana, and the Master.) can exert willful control over the regenerative process, and thereby control the nature of the new body’s form, and reduce profound personality changes. It also bears mentioning that in certain circumstances, a Time-Lord may also encounter a temporal projection of his potential future-self. This happened to the Fouth Doctor as his regeneration drew close, as he found himself shadowed by a mysterious, pale being identified only as “The Watcher” by his companion, Adric. The extremely wise and ancient Time-Lord, The Abbot K’Ampo Rimpoche, had consciously projected his future-self in the form of Cho-Je, the monk in charge of the Abbot’s Tibetan Monastery. When K’Ampo regenerated, he assumed the physical appearance of his projected self. However in his case the projection was a conscious, fully-formed one, in stark contrast to the nearly featureless “Watcher”.

The Doctor, in contrast, has displayed time and again the symptoms of problem regeneration. For him it has always seemed to be something of a struggle, both physically and mentally. In fact on 3 separate occasions the Doctor would not have survived had the regeneration not been pushed by outside forces (The Doctor’s first regeneration was assisted by the TARDIS itself, the 2nd had to be activated by the Gallifreyan K’Ampo, and the 3rd was facilitated by the aforementioned Watcher). Thus far, the Doctor has regenerated 10 times, resulting in 11 different incarnations. Every Time-Lord is able to regenerate 12 times. After that, the final regeneration is fatal, as the body (or perhaps just the brain) can no longer survive the strain of such radical change. It also bears mentioning that the Regenerative process can be inhibited and possibly destroyed by certain types of anesthesia, a problem that helped “kill” the Seventh Doctor and inhibit his regeneration into his Eighth incarnation.

Ordinarily the final regeneration would mean the end of the Time-Lord in question, although before Gallifrey’s destruction at the end of the Last, Great Time-War, the Time-Lord’s knowledge and biodata lived on in the APC Net (aka “The Matrix”), recorded and stored before final brain-death. And, in certain dire circumstances, long-dead Time-Lords have been resurrected by unknown means. Time-Lords that have been brought back include the Master, who was resurrected in order to help fight in the Time-war, and the great Time-Lord President, Rassilon, who also seems to have been brought back for that very same reason.

With the Doctor currently in his Eleventh incarnation, it would at first seem that his end is approaching, as ordinarily he would have only two incarnations remaining. However, there are indications that such may not be the case. As the dying Tenth Doctor staggered to his TARDIS, having held off his impending regeneration for hours (or perhaps days) by sheer force of will, Ood Sigma stated “This song is ending, but the story never ends”, a somewhat cryptic remark that suggests the Doctor’s “song” will never end, and that he may live on in some form for the rest of time. I would be remiss if I failed to mention that it has been suggested (Mainly by the Doctor himself, during his Seventh incarnation) that the Doctor may be something more, that he possesses powers and knowledge far beyond the average Time-Lord. There is some evidence to support this claim (see the “Cartmel Masterplan”), but not enough to make the assertion a proven one. However, the ground has been laid to suggest he may indeed have the ability to survive through countless, perhaps perpetual, incarnations. Considering how well the series has done since its return, it would be foolish to assume that should it continue to do well, that the series would end with the “death” of a future Thirteenth Doctor.

Personality

Although the Doctor’s actual personality has varied wildly from incarnation to incarnation, there are some constants. The Doctor’s basic morals have remained rather rocksteady throughout his adult life. The Doctor despises injustice, and rarely hesitates to act when faced with it. Nothing can stir him to action like the sight of oppression, and it is this trait which has caused most Time Lords to consider the Doctor an embarrassment and a renegade. He will do everything he deems necessary to counter it, usually trying to find the least violent means possible (the Doctor never carries a gun, and while he has used them on various inanimate objects, he’s loathe to do so). Most of the Doctor’s incarnations hated violence as well, although a few of his incarnations could dispense non-lethal, two-fisted justice if it seemed a good thumping was needed (Notably his third and fourth incarnations, and his sixth knew some hand-to-hand tricks as well). Because he usually avoids violence in times of conflict, the Doctor often uses his charisma to end friction, and can become extremely commanding and authoritative should friendly persuasion prove insufficient. He is usually capable of swaying all but the most skeptical or evil beings to his cause, which is good because the Doctor finds himself in tense situations quite often.

The Doctor is insatiably curious, and displays a great love and hunger for knowledge and new experiences. There doesn’t seem to be any school of thought where he doesn’t possess at least some basic knowledge. His knowledge of the sciences and history are particularly acute. This trait is one that seems to get him into the most trouble, as he can rarely avoid investigating a mystery or a troublesome quandary. He is capable of brilliant improvisation when he finds himself in a difficult spot. Perhaps because of his long-life, and his vast knowledge, the Doctor can be quite arrogant at times, showing little patience for the failings of ordinary mortals. At times he has referred to homo sapiens in less than complimentary terms, using terms such as “stupid, little people” and “stupid apes” to describe humanity as a whole.

That said, in his defense, it must be stated that with his vast age, knowledge, and time-sensitive perceptions, human beings must often seem like children by way of comparison. Thus, his oft-expressed admiration for and patience towards his “favorite species” is rather remarkable considering his perspective. He deeply believes that humanity is capable of much more, and considers mankind to be ultimately “indomitable”. Because of this belief and because of his nature, the Doctor has become the Earth’s unofficial protector and advocate, and won’t hesitate to stand in defense of his adopted, second home. Capable of great compassion, he rarely hesitates to risk his own life for his friends, or for those in need.

The means by which he fights injustice and evil can vary from incarnation to incarnation. The First Doctor tended to think and plan very carefully before acting, but his intelligence and wisdom would soon become quite apparent. Two tended to act silly and fearful in order to manipulate his enemies into a position where he could defeat them. Three was a man of action, ready to jump into the fray and take immediate command of the situation. Four played the fool much like Two, but had a more commanding presence and an eccentric approach that kept his foes off-balance. Five was somewhat vulnerable and occasionally passive, often getting swept up into events against his will. However he could improvise brilliantly in a pinch. Six was mercurial, loud, darkly humorous, and temperamental, but steely and determined in the face of danger. Seven was very much like Two, but where his second incarnation was reactive, Seven was proactive. He would maneuver friend and foe alike like pieces on a chess-board until the time was right to strike. Eight was poetic and soft-spoken, vulnerable in ways similar to Five, but very perceptive about the people around him, and how they fit into the larger scheme of things. Nine was energetic, and usually friendly, but quick to anger and tended to be sombre. Suffering from deep survivor’s-guilt and loneliness in the wake of the Time-War, he would sometimes enlist the aid and suggestions of those around him before deciding on a course of action. Ten possessed almost boundless energy, a verve to explore, a mouth that wouldn’t quit and a mind like quicksilver. He would offer his foes a chance to surrender or retreat, and if they failed to take it, his reactions were swift, ruthless, and decisive.

If you could sum him up, the Doctor views life as a gift, and freedom as sacred. He will fight unceasingly for the preservation of both with all the knowledge and power at his command. He stands not only as Earth’s champion, but as the champion of life and liberty across the whole of the cosmos.