I agree with what I think you’re asserting, that the number of variables that might contribute to triggering any sort of event is incalculable, but as a matter of practicality, I assume we have to view causality as a gradient of probability. In other words, we account for as many variables as we can, and make a “best guess” based on what we know. We can make “predictions” based on that until we know more, and then we redefine our overall system over time.

Edit: a word