According to the "Allegory of the cave" by Plato, what is reality and what is mere illusion?

Plato's allegory of the cave Analysis

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

Explanation:

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frederick william of brandenburg-prussia trained his son, frederick, to be a hardy soldier. but frederick disliked rifle shooting and horseback riding. unlike his father, he was interested in french literature. he enjoyed poetry and music and, like some others of the enlightenment, he scoffed at religion. his father thought him soft, frivolous and unmindful of his duties. and when frederick refused to put his signature on a right to succession, for a few moments his father strangled him.