What I was getting at is it seems Buddha didn't get into what is a cause and effect. Again I say in disagreement though, karma does not mean 'cause' it means 'action.
Yes, karma means "action." But there are other terms to consider. It might be useful to differentiate some of them. In the Nikāyas and Āgamas we find the terms hetu
) often used as synonyms. They are commonly translated into English as "cause" and "condition" respectively. For example in DN 15 we find these terms used together in the explanation of dependent origination as follows:
Therefore, Ānanda, just this is the cause (hetu), the source (nidāna), the origin (samudaya), the condition (paccaya) for ageing and death, namely, birth ... the condition for birth, namely, becoming, etc.
In the Sarvāstivāda Abhidharma the terms hetu
are further developed into the six causes and four conditions.
Other relevant terms are phala
(fruit) and vipāka
This a Dzogchen topic so lower yana terms are not going to work the same. In Dzogchen nyingthig there's the notion that all is rigpa. You don't have this in the Hinayana. Dzogchen puts the lens to the inner world exclusively because there's no inner outer duality. That's why it's the path beyond cause and effect.
But to comment on your quote: There is this notion of causes and conditions in Buddhism. But there is no real theory of causality coming from Buddha's mouth. Your quote is saying (paraphrasing) "It's the cause, source, origin, condition, or whatever you want to call it." And he uses these terms interchangeably. A theory of causality would specify how these terms are to be used. For example, conditions precedent versus conditions subsequent or concurrent. Proximate cause, actual cause, contributory cause, etc. Hume couldn't succeed in isolating any of this and no one has improved on his work. No scientist has. There is actually to this day no valid theory of causation. That's really one of those remarkable cues to wake up from the dream of existence.
So, because we are working with loose terms, we can't treat them as hard and fast terms. Yes there are actions and fruits, the actions cause the fruits, and the fruits are the conditions for more actions. That we get. We can sort of leave it at that. We don't need to get deep into these notions because they don't lead to anything like liberation. Instead, they lead to endless intellectual analysis, prapanca. Especially to a newbie with a fully indoctrinated science view, these ideas are what make Buddhism a palatable religion. There's something more 20th century in Buddhism and less pre-modern era, something quantum. As soon as you go to look for the cause, i.e., desire, you don't see it. As soon as you aren't trying to see it, it comes on strong. Or you can say once you have habit of behavior under the lens, you don't find it. What is a behavior? Action. And action per Nagarjuna is emptiness.
So just to reiterate what my main point is, it's inside of us where our minds should focus, not on theories in books.