What, if anything, makes forces the "cause" and acceleration the "effect"? We typically say that forces cause acceleration inversely proportionate to mass. Would it be any less correct to say that acceleration causes forces proportionate to mass? Why?
(Note that the underlying question in my mind - essentially, what distinguishes cause from effect - is far more general. But this seems like a good place to start.)
 A: Newton's first law states that an object will keep doing what it is doing if left alone, in other words - The natural state of an object is static - unchanging - motion. 
Newton's second law clarifies the first. Acceleration, or any change in motion, is an unnatural state for an arbitrary object left to its laurels, however it is a state that clearly exists all around us. Newton defines the "thing" that forces an object to change its state of being - a force.
In this most rigorous sense, a force is defined to be that which causes a change in motion.
The observation of a change in momentum necessitates that there is some force driving that change, so in this sense the two are equivalent (there is an equals sign there after all) - wherever you see a (net) force you will see an acceleration, wherever you see an acceleration you will find a force responsible for it. However, going back to the first law, acceleration is a change in the (kinetic) state of an object, an objects natural tendency is to statically maintain its state. The observation of an unnatural state of being would logically imply that there is a cause.
Intuitively it seems unnatural that accelerations would happen spontaneously and that the universe will invent a force  just to balance the books if you will. 
A: I hope @Toph is not jesting whit this question but I will bite. There are 2 actions and effects when a force is applied. Say Object A pushes on object B the 1st cause/effect is that B resist moving “Static Resistance.” It’s apparent here that A courses the effect that B will resist. If B does not move then the effect is all on A and the energy is dissipated in heat and A stops. If B does move then is because A transfers the force to B or B takes the force from A. The only reason I contemplate this is that the more I learn of quantum-mechanics the more I wonder if physics of the big are what they appear to be.
