A good statement that is an example of a major counterclaim to address in an argumentative research essay with the claim: "All schools should be equipped with metal detectors" can be that installing metal detectors would be a too high cost to afford for most schools. Because it is not only the costs of metal detector machines, but also there must be a security man controlling the machines, and if schools could not afford these costs it should be provided by the state government.
The 'Allegory Of The Cave' is a theory put forward by Plato, concerning human perception. Plato claimed that knowledge gained through the senses is no more than opinion and that, in order to have real knowledge, we must gain it through philosophical reasoning. Imagine a cave, in which there are three prisoners.