You can define a category any way you please; the question is, what useful attributes and predictions are common to all members of the category. I either don’t understand or don’t agree with your distinction between categories of causes and of effects.
For instance, if you can claim that all things causing effect Y also have a common attribute X, that’s a legitimate category that makes a useful prediction—even if there’s no single mechanism underlying the relationship.
The real problem with the argument you quote seems to me to be that the statement “there are two forces that act on humanity” is not useful. It’s either tautological (“various things have happened in history; some of them have brought us together, and some others have driven us apart”), or meaningless and/or wrong (“everything that ever happened to humanity either brought us together or drove us apart”) or just useless (“both the fall of Rome and the Black Death drove us apart, for a suitable definition of “drive us apart”, but that’s the only thing they had in common”).
You can define a category any way you please; the question is, what useful attributes and predictions are common to all members of the category. I either don’t understand or don’t agree with your distinction between categories of causes and of effects.
For instance, if you can claim that all things causing effect Y also have a common attribute X, that’s a legitimate category that makes a useful prediction—even if there’s no single mechanism underlying the relationship.
The real problem with the argument you quote seems to me to be that the statement “there are two forces that act on humanity” is not useful. It’s either tautological (“various things have happened in history; some of them have brought us together, and some others have driven us apart”), or meaningless and/or wrong (“everything that ever happened to humanity either brought us together or drove us apart”) or just useless (“both the fall of Rome and the Black Death drove us apart, for a suitable definition of “drive us apart”, but that’s the only thing they had in common”).