You are changed by the intention behind your decisions. Someone who continually chooses to do things out of greed turns into a greedier person. Someone who continually chooses compassion becomes a more compassionate person.

Even if the external outcome is the same, the direction towards which the person evolves is vastly different. And when lifted out of a narrow thought experiment, in real life, who you are does determine all the great and small ways you behave, and the methods you are willing to employ.

That’s why in the Sermon on the Mount, Christ says “It was said to those of old, you shall not murder, and whoever murders will be liable to judgement. But I say to you that everyone who is angry with his brother will be liable to judgement.”

You will find similar principles expressed in Buddhist teachings, or the Bhagavad Gita, or Confucian ethical philosophy. In this instance, anger on its own is merely a seed. But if left to grow, and it grows by you watering it, then eventually it expresses itself in a much more destructive way.

Maybe this is how it works, but how can we know this?

It could also be that doing good things for selfish reasons creates habits of doing good things, and after a while that is who you are and what you do.

There’s some real research into relevant topics and evidence-based models of how and why people change.

Generally, a period of ambivalence precedes change (most of the time, though there are documented cases of “quantum change” where a person undergoes a difficult change in a single moment without the usual intermediate stages and never relapses).

Ambivalence exists when a person knows in their mind reasons both for and against a change, and gives both more or less an equal mind share.

When that person begins to give an outsized share of their attention to engaging with thoughts aligned with the change, it predicts growing commitment and ultimately follow-through on the change.

The best resource I know of on this topic is “Motivational Interviewing” in its 3rd or 4th edition. It has a very extensive bibliography and the model of change it presents has proven itself an effective predictor of change in clinical practice.

Based on my understanding of that research, I’m inclined to agree with GP.

That's very insightful. Could you share some references for further reading? I'd like to explore this topic a bit on my own.

The main resource that I recommend is the one towards the bottom of the comment: “Motivational Interviewing” by W.R. Miller and Stephen Rollnick. I’ve read the third and fourth editions. The third edition is more concrete but also more complex, and more focused on the field of clinical psychology, while the fourth edition is a shorter book where it’s been generalized more to be more applicable to all kinds of helping relationships, but contains fewer specific examples of clinical practice.

In the second edition they had not yet broken up the concept of “resistance” into “sustain talk” and “discord,” which I found to be a helpful distinction.

About 10% of the book is its bibliography, so if you want more information about a specific claim you can usually find the primary source by following the reference.

Miller and Rollnick are the ones who developed the technique of motivational interviewing, so they have a strong connection to much of the research cited.

There are multiple ways, all of which are useful for you to decide whether it's true or not.

First, you can trust in the wisdom of those who came before you, i.e. scripture. Second, you could trust in tradition, which may say such things. Third, you can use reason yourself. Fourth, you could rely on personal experience.

Another way to think of it is:

If you tend to engage in suspicious behavior, you'll probably start regarding others with suspicion. Essentially, your actions will engender your world view.

This is a good take, and I agree that habits can do that to people.

On the other hand, the intention behind the habit/action easily twists it in actuality to something else.

I think the “fake it till you make it” I brought up upthread a great example of this. Yeah, it might end up with the fake becoming something valuable, or you building character, or whatever.

Or, the habit that is getting built isn’t positive hustle and tenacity, but just a habit of outright lying, constantly reinforcing itself.

Sometimes it’s impossible to see from the outside what is which until it breaks down.