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Well, let's see... It's very tempting to play with this kind of question, but I'll answer it seriously.
Because the methodology (calculus) for conceptualizing the infinite is used to design, run, and theorize most of the industrial and post-industrial world.
For example, Renaissance perspective, the theory of ballistics, and projection maps of the earth all depend on the same mathematical ideas that were developed to conceptualize infinity. The list of practical applications is almost endless. The same methods used in statistical mechanics also provide the means to measure the effects of various political propaganda campaigns or make economic policy appear to be a `natural' phenomenon rather the deliberate machinations of the power elite. I don't know. Pick your poison, the calculus of infinities will be there.
Besides the life of the mind didn't begin or end with Marx.
And then too, one never knows when knowledge like this will come in handy. For example, Joanna, who brought this up in the first place, also claims to be a good shot. Maybe there is a connection...
Practical question. How to you drop a fat Repugnant from four hundred yards running at a 45 degree angle way from you?
Practical answer. You don't lead them as much as a thin Repugnant.
Theoretical answer. Two independent functions in real coordinates (x,y,z,t) must be solvable for the same coordinates at (x',y',z',t').
CG