To what extent does regeneration involve a timelord's fundamental personality - or vice versa?

The Doctor, for example, changes physically and there are some obvious and striking changes to his personality when he regenerates - but there's a basic part of him that is consistent to the regens we've seen - such as his bravery, intelligence and compassion.

The question is - does a timelord have some sort of unchangeable "soul" that is common to all of their regens or can they change EVERYTHING about their new persona at will?

For example - could a timelord deliberately chose to regenerate as a murderer?

Wouldn't The Tardis have a say and ensure The Doctor's regeneration and personality is as The Doctor should be. Essentially maybe if The Doctor is time itself, would time exist as was shown in The Wedding Of River Song when the clocks stopped?

I'm not sure if this answers your question, but according to the audio The Sirens of Time (which I've not actually listened to, I've just read about it), the "nurture" part of a Time Lord's personality, i.e. their primary character traits, remains the same, but the "nature" part, i.e. their secondary character traits, does not.

I don't know whether the former is a choice they make or if it's that way by default. As for whether they could regenerate as a murderer I guess that depends on whether nature or nurture are responsible for making people murderers (which is another topic altogether).

My opinion is that the Doctor's core doesn't change - his beliefs, values, intelligence, remain the same. His personality can change. He can become grumpy, rude, less compassionate to others, less caring of the feelings of his companions. In time, he can adapt to his surroundings and adjust his personality to social norms so that he doesn't drive his companions away. In other words, he sometimes is like a child and has to learn to work with others.

Even in the "Snowmen" Smith's Doctor was in a snit and didn't want to help anyone until Victorian Clara thawed his hearts and made him realize that he missed being with someone.

As to making a choice to regenerate into a murderer? That would be a choice of reason, not a choice of body. The choice of being a murderer would have been made before a regeneration and could have been done even with the previous body. Anyone can be a murderer. It is just a choice. It is just not one that the Doctor would make willingly. He has killed to protect others in self defense. That is not murder. The Time War is a close to Murder as he has gotten and we are going to see the result of that decision in the 50th Annv. Special and I think with the JH Doctor.

Technically he was guilty of two counts of genocide. First he destroyed the time lords to end the war taking Galifrey with it. Second in TEOT 10 stoped them returning thereby condeming them and his own family again. Time lock resealed itself putting everything back. Untill we saw the "other" doctor. Reckon there is more to the story.

But the time lords were ready to destroy the universe so by locking them into a time lock, which did not kill them, just froze them in time. Since they are not dead, there is no genocide in either case. End result was that he saved the universe from his own people.

I could NEVER chose" be a murderer anymore than I could "chose" to be short and fat.

I might be able to kill someone in certain circumstances but I could not MURDER without totally changing my base personality. There is a VAST difference between killing and murdering.

In a situation where the ONLY solution to a problem involved murder - I would be powerless UNLESS I was able to totally rewrite myself - to regenerate at a personality level.

Besides, you are focussing on what was clearly just AN ILLUSTRATION of a point. Try to see the bigger picture - and the question is - can a Timelord change his/her CORE PERSONALITY if necessary - as in, can he/she become a completely different person.

And I have to point out that the Master became a "nice person" just by using his pocket watch - so it's not THAT daft a question.

I didn't think the question was daft, and I do think that the core personality does not change during regeneration.

As to the Master illustration, that is using an external device to stimulate different emotional responses, it may not be changing the core personality.

As to the argument of the choice of being a murderer, I will leave it there. I believe that people have a choice in the matter. I do agree with your statement that there is a VAST difference between killing and murdering.

In that case, I'm going to have to step in and be the dissenting voice. There's a tiny difference between killing and being a murderer, and it's a line that the Doctor has sailed close to many times. Some might say he's crossed it a few of those times.

Was the fate of Solomon the trader a killing, an execution, or a murder?

As for the Time Lords, being trapped in an unending hell of death and insanity is at least as bad as being dead.

Different actors play the fictional role. Their personalities are different. That is about it. I wouldnt have wanted 11 actors to try n act as Hartnell's personality. Obviously as actors they work with the showrunner to create their own persona.(Im a fan n not trying to be horrible-it is the way I see it)

You have really hit upon the truth of the matter. The Doctor dislikes thinking of himself as a person that deals in death, yet he causes the death of others. He knows that he does it to saves others, he gives those he is about to kill a chance, but he will kill to save. He grieves and it hurts him to kill and that is what keeps his humanity alive.

Who says that is the case, maybe The Time Lords can choose to correct this by destroying the myth that is The Time War. If the myth has continued through time itself, has The Doctor been just the reminder of it's so called existence because he remembers the so called Daleks .

The real problem is that the Daleks survived and the only Time Lord to survive was the Doctor. Now that Clara in the form of an insane Dalek wiped the Doctor from the Dalek's memory, the Doctor could try to come to some kind of truce with the rest of the Time Lords.

But then the rest of the Time Lords probably want the Doctor dead for locking them away just as much as the Dalek's want the Doctor dead (if the Dalek's could now remember who he was). It would be a double burden to be hated by both your enemy's and by your own race. He has always been an outcast, but now to be hated is a terrible thing.