Can people change their behavior?

Temperament sets the range a person moves within, and the range does not shift

Question: Can people change their behavior?
Position‹2 of 2: No, people cannot change their behavior
Argument1 of 2›: Temperament sets the range a person moves within, and the range does not shift

The argument

Proponents of this position argue that behaviour is downstream of something steadier than behaviour. Dispositions, how readily a person is angered, how much risk they will tolerate, how much order they need, how far they are drawn to novelty or to company, show up early, before upbringing could have installed them, and are recognisable in the same person decades later. Those who have known someone since childhood are seldom surprised by what they do in middle age. If that is right, the argument runs, then what can be worked on is narrow. A person may learn to manage a temper, but not to stop having one; may learn not to act on an impulse, but not to stop feeling it; may acquire the manners of patience without acquiring patience. These are real achievements and worth having, but proponents insist on calling them what they are: better handling of an unchanged disposition rather than a change in the disposition. The pressure is still there, and it shows under strain, in exhaustion, in drink, in crisis, when the acquired management is the first thing to go. The practical upshot, on this view, is that people should be judged on the record rather than on their intentions. Someone who has been unreliable in every arrangement they have entered is unlikely to be reliable in the next one, however sincerely they resolve to be, because the resolve is not operating on the part that produces the behaviour. Proponents hold that the hopeful view of change persists because it is pleasant, and because it flatters both the person resolving and the person forgiving, rather than because the record supports it.

Premises

[P1]Dispositions such as temper, impulsiveness, risk tolerance and need for order appear early and persist across a life. [P2] Behaviour follows from those dispositions, so effort can manage their expression but not remove them. [P3] Managed expression characteristically fails under strain, revealing the unchanged disposition beneath it. [C] Therefore people do not change their behaviour in any deep sense, and the record is a better guide than the resolution.

Counter-arguments

Opponents reply that the argument wins by definition: any change achieved is reclassified as management of an unchanged disposition, so no evidence could ever count against it. They add that a person who manages a temper for the rest of their life, and whose family never again sees it acted on, has changed their behaviour in every sense that matters to anyone affected by it. If the thesis survives only by declaring that kind of change not to be change, it is a claim about a word rather than about people.

Rejecting the premises

[Rejecting P1] Early-appearing traits are described as tendencies across many people, and a tendency that holds on average is consistent with substantial movement in particular lives, which is what the question is about. [Rejecting P2] The step from disposition to behaviour is where the argument needs most and shows least. People of similar temperament live very differently, so a great deal is settled after temperament has had its say. [Rejecting P3] Exhaustion and crisis are the hardest conditions anyone faces and a poor standard for judging a change. By that test no skill is ever learned, since every skill degrades under strain. [Rejecting C] Advising that the record outweighs the resolution turns the thesis into a policy that makes itself true: treat people as unable to change, and the conditions under which they might are withheld.