Question

Hello Rabbi, I would like to raise a general question. I would be glad to receive from you perhaps a broader theoretical discussion of this question (philosophical sources), and if possible also examples in Jewish law of when each of these approaches is used regarding the practical question of what should be done. Ultimately, I would also appreciate guidance as to how you think one should decide between the alternatives.
When we come to decide what the proper act is, two possibilities stand before us regarding society’s relation to the matter.
1 – We decide according to what we think would make the world better if everyone decided that way (without getting into the question of what “better” means).
2 – We decide according to the state of the world as it is now; that is, given that it is not actually common for the world to behave this way, even if this is not an act that we would think it proper for the entire world to adopt.
I’ll give an example (of course, let’s stick to the logic and not the substance of the example):
A person thinks that the rate of population growth in the world is such that it prevents human beings from achieving a sustainable way of life, and that the world would be better if the population size remained constant.
Ideally, he thinks it would be good if every couple brought two children into the world, so as not to increase the population. According to the first approach, he would have two children because that is how he thinks everyone ought to act. According to the second approach, he would have no children at all, or only one, taking into account that the average birthrate in the world is higher than 2.
I am aware that this question is very close to the question of whether the intention behind an act is important or its consequences, but it is not the same question, because here, according to both approaches, it is the consequences that matter. It is just that the first approach says that a person should do his part and no more, that he has no obligation to “balance out” something in the world, but rather to set an example of how everyone ought to act, perhaps as part of each person’s role in establishing norms. I am also interested in what happens from the halakhic side. Seemingly, it is convenient to argue that Jewish law sets a norm, meaning what is expected of everyone to do, and therefore would not take into account what the broader public generally does. But that too is not correct, because in many places there is consideration of what most people do (for example, with the minor fasts when most of the Jewish people are in its land, there is an opinion according to which the obligation derives only from the fact that the majority of the public fasts, but ideally the obligation to fast no longer applies).
Thank you very much…